Love the theme!
How about a B scavenger hunt? A list of things to find that start with the letter B - bug, ball, bandana, broom, bracelet, butterfly, bell, book, etc... Have a picture next to the word for kids that aren't strong readers.

While they're sitting waiting for food/cake, give them B themed coloring sheets.

A cake in the shape of the letter B with some icing bees on it might be easier than a bumble bee cake.

Have fun, and happy birthday to your guy.

AM

I expected it to be "Bobby's Big Boy Birthday Bash"! :)

It's a VERY cool idea! and it sounds like you have it well planned already.

On the banana "bumblebee" cake (also a great idea!), I would consider using two round pans of different sizes. The larger round would be the body and the smaller round his head. I'd try making some waxed paper wings to tuck at the base of his head -- might need to glue or tape a little veining or support pieces to hold it in the cake. I think it would work! I can certainly envision it. lol!

Amazing....I went to a "bee" themed birthday party for a 4 year old on sunday! LOL!
The mom made the cake out of one of those pudding cake mixes, baked 2 layers and froze them. and while they were frozen shaped them into a sort of dome shaped bee body. She then filled it with some yellow tinted butter cream ( from a can she said!) made stripes with some black frosting also from a can...and used licorise sticks for antennae and some sort of other candy for the eyes.
This was a little girl's party so they made bee costumes out of paper bags and wore bee hats with antennae and played pollinate the flowers and gather nectar. some kids were flowers with a paper flower lei and others were bees and it was a chase game!
Have fun!

This is a cute 'B' is for bear concept - perfect for a kids party

What about doing the letter B but also a color theme? Maybe Blue and Black?? You could find a cute banner on etsy I bet. I found some really cute party decorations for my daughters puppy themed party on there.

Anna
http://wastedbandwidth.org

Well, the party was a success so I thought I'd share the results after your thoughtful replies.

Invitation:
Cut out a large letter B from paper printed with balloons. I randomly wrote on the front B=Ball, B=Balloon, B=Book, B=Bubbles, B=Bugs. Then I wrote the party details for the Big Boy Birthday Bash on the other side, including that this was a "B" themed party.

Food: (I was cooking for about 43 adults and kids.)
Beefy Ribs and (Buns with Hotdogs for the kids)
Brown Rice and Chickpea Rainbow Salad (GREAT pesto vngrte)
Beans with Lemon and Walnut Vngrte
Bacon and Blue Cheese Mashed Potato Casserole
Biscuits with fresh herbs and Basil Butter

Drinks:
Basil lemonade
Blueberry lemonade

Cake:
Banana cake in the shape of a bumblebee. I found a baseball cake pan the shape of half of a ball and thought "why not make that the body of the bee?" So I did. I used a 6" round cake for the head, but I cut it out a bit to fit snuggly into the round body cake piece. I frosted it with golden yellow buttercream. I was in a hurry so instead of mixing black icing for the bee's stripes, I sprinkled on brown jimmies in stripes. I used black licorice for the antenna and legs. I made wax paper wings with popsicle sticks as veins. I found those black licorce wheels as big eyes. It was so cute!! And tasty! Since I needed cake for 43 people, I made some extra banana cupcakes frosted with the bee frosting and some jimmies.

Games:
Balls (football, baseball, tennis balls, curvy ball and catchers, bouncy balls, soccer ball, beach ball, etc.)
Bubbles (FIL makes his own bubble juice and has tons of fun wands)
Butterfly pinata (couldn't find a bumblebee) filled with small bouncy balls, bee rings, etc.

Treat bags:
Black Bags filled with small "B" items like bubbles, ball erasers, blowers, etc.

Decorated the house and deck with tons of balloons from the Dollar Store. Some of the gifts given to DS began with B, and some even decorated their gift bags and cards with B. It was cute to see people get into the theme.

All in all, it was a great party. Kids had a fabulous time--too much of a good time at moments. ;)

Thanks for your help!

Great party! So much love and planning in it. I'm sure the kidz had a great time. Thanks for "inviting" us!

So glad you came back and shared the results - it sounds like a fabulous party!

And, would you mind posting that Rainbow Salad recipe? Looks like a keeper.

AM