Wow that sounds like a huge celebration. What fun!
It sounds like you're going to have your hands full planning this shindig, so if it were me, I'd buy the invitations and decorations. Other than what you're planning already, I'd dress the boys up as Woody and Buzz. If you have a Mr. Potato Head you could have a contest to see who can assemble him correctly the fastest- while blindfolded. That's my contribution. Make sure to post pictures of the party!