I don't think you will need to make ingredient lables for the dishes. When sticking close to certain food guidelines is important, most people place the responsibility with the eater, not the provider of the food. Your party is small enough that if your guests desire, they will be able to ask you "What's in that?"

For most dishes, it is rather obvious what sorts of ingredients are used. Try to avoid "hidden" ingredients. If you use ground almonds in a cookie recipe, decorate the top of the cookie with almond slices. If a vegetable recipe calls for wine or chicken stock, substitute vegetable stock. When cooking, be sure to use a clean spoon for each dish so that you do not do something like get walnut oil in the vegetable soup. A vegetable platter and a cheese and cracker platter will offer something for almost anyone without any hidden surprises.

Be careful with cracker and bread selections - there are a lot of them that contain peanut oil. Due to the nature of nut allergies - some people can have life-threatening reactions to just a minute amount - I have personally opted to eliminate all forms of peanuts and tree nuts (these are two different allergies) from my home. My son has multiple food allergies - we aren't sure about nuts as he has so far never encountered them - but his doctor has adviced us to keeep him clear of them until he is older. Anyway, recently I made a cheesecake with a pecan crust... Those pecans crumbled everywhere. Then I ran my food processor (which I had chopped the nuts in) and the cheesecake pan through the dishwasher and had little pieces of pecans stuck inside my son's drinking cups (the little non-spill valve). That is when I decided - for me - it was just easier to avoid nuts completely than to work around them and try to keep them clean and separate. To someone with severe nut allergies, even the residue oils from nuts can cause a life-threatening reaction. That said - Duckie's advice regarding 'hidden' allergens is excellent - if you decide to make something with nuts, make it obvious! And do keep all your cooking and serving utensils super clean.
Lactose intolerant - they can generally take med prior to eating to control the majority of that problem. Processed foods are awful about having hidden milk protiens - especially deli meats, prepared meatballs, crackers, etc. (I cannot find a single ground meat product that my son can eat as they all have "natural flavors," "carmel coloring," etc. that can mean they contain a dairy product.)
Vegetarian - depends on the type. Vegan means no dairy or eggs, which can be difficult to work around. However, if they are lacto-ovo vegetarian, that just means no meat so your cheese platter and dips are fine.
I wouldn't go to the bother of doing ingredient list, but would perhaps make simple signs, like Almond Cookies, Beef and Pork Meatballs, Rum Cake, etc. - just enough to let people know in general what is in the food.
If all else - do ask them. I would love it if someone asked me what my son could or could not eat, rather than them inviting us over for pizza and having nothing for him to eat! Also, if they ask if they can bring something, allow them to as they will likely bring something they can eat.
(Rant: My FIL and his wife recently invited us over for supper... I kept offering to bring something - they kept refusing. Mind you, they know about my son's food allergies. Luckily, I did take food for him to eat. But do you realize how hard it is to keep a one year old out of pizza?! He didn't want the food we took him so the whole evening was a battle getting him to eat his 'safe' food and keeping him out of the pizza. Now we are invited over for a pizza party at Christmas time... I don't know what we will do.)
Best wishes on your party. ~ Suzie

Most people I know who are specialized with their diets range from diabetics to vegetarians. I usually try to have fruits and veggies, as well as pasta dishes around to accomodate them easily. I would not try to also accomodate diets such as Atkins.

Even my specialized friends did not expect the world to revolve around them, although it is admirable of you to try and accomodate. They already know what to choose, and especially with the diabetics, make it a point to eat something on their own prior to attending parties and potlucks.

Thanks for the suggestions everyone. At least I already know that one person is allergic to Hazelnuts and one person is allergic to peanuts (so I know what to avoid there). I'm figuring a fruit platter will be good for most of the attendees. Maybe some salmon for the Atkins person. I have a lactose problem as well as one of the attendees so I will know myself what items have dairy in them.

I think I'm going to keep my own party journal from now on and log what everyone is allergic to and what they did or did not eat. I actually find it very interesting how everyone is dealing with their allergies, etc. It makes me realize that people who I once may have considered "fussy" are actually protecting their health. ...and now that I have a few health problems too, I am very fussy myself with how I grocery shop now.

I have parties with people who also are on various diets. One is vegan, one won't eat land animals but will eat dairy and seafood, several are on weightloss diets that are low fat, some don't eat veggies except for beans....

I've been successful with Mexican-themed parties. Last one was a taco menu. I made steak filling, shrimp filling, and a veggie filling and the regular fixins all in separate dishes (couldn't have the cheese contaminate the veggies). Also had fat-free refried beans, vegan black bean soup, and various salsas and cheeses. It was pretty obvious to the vegan and the non-land-animal-itarian which stuff to avoid. All the foods were realtively low-fat except the cheese. So it worked out well. The steak filling would work for an Adkins person, they just wouldn't use the taco shell. Could use soy cheese for the lactose intolerant.

Try a Japanese theme - no lactose and most foods are separated so that Atkins people can keep carbohydrates out when required.

Soy cheese is pretty bad, IMO, at least if it is melted! I think it is a good idea to keep cheese separate at a party - that way people can avoid it if necessary, and it doesn't need a label. Don't serve ranch dressing with milk either. Simpler is better.

Lars

Wow... that was definitely a party challenge! I would have gone a simple buffet route, no nuts in anything, big salad with oil & vinegar dressing , fruit and vegie tray, a hot vegie, potatoes, chicken/roast beef/ham, bread, and something for dessert. Diabetics know what to eat or not eat, lactose intolerants can ask, vegetarians can skip the meat, and the Atkins people are on their own to figure it out. I would NEVER expect to go to a dinner party and have ALL my dietary oddities catered to.

Suzie-- In the future, always feed your son BEFORE you go to the inlaws. He won't be as hungry, and you can give him his favorite snacks in lieu of pizza. When the inlaws comment on how you're letting your child fill up on "junk" you can remind them that they have not otherwise accommodated your their grandson's food allergies. LOL My only other suggestion is to wait until after dinner to meet up with the family; I know how stressful it is to "reason" with a toddler on what he can and cannot have!

I'm glad I asked ahead of time for my upcoming party. The son of one of my guests has dairy and peanut allergies. I'm having penne ala vodka, pasta primavera, and beef as hot dishes, and also cold cuts. I think he should be able to have something from this. I'll also see if I can come up with a dessert for him.