For your menu choices, I think harvest and comfort foods would be nice: like a beef stew, with field green salad with cranberry vinagrette and thick slices of multi grain bread.

For a nice finish, a spiced carrot cake would be perfect, ask your baker to decorate the cake with frosting or marzipan decorations to compliment your decor (autumn leaves, pumpkins and fall-color flowers). OR go really different - a bread pudding with rum sauce maybe?

Consider serving a fresh chilled or hot mulled cider with your appetizers and/or dessert.

Hard to say what kind of food. I would pick what your mom loves best -- keeping in mind what your guests will enjoy, too. If she's a baseball fan, for example, have hot dogs and peanuts and beer. If she loves travel, have exotic choices.

But I think really your best bet is to give the caterer a budget and let him/her suggest things. That always works for me.

For decorations, flowers always say "special occasion," but they can be expensive. You can make copies of photos of her at different stages of life and put them in inexpensive lucite frames of different sizes (you may even be able to ask the store if you can return them if you keep them in perfect shape) and put a few on each table for centerpieces, perhaps with a single flower or candle. We did that for my mother's 70th and it worked nicely. Potted flowering plants with a ribbon around the pot are also nice and inexpensive centerpieces (and a lot less work). You can give them as thank you gifts to people who help you with the party.

You are so nice to do this for your mother! Good for you. I am sure she will be thrilled.