C.W.
I wouldn't do nothing that big since he really doesn't have a clue. For our son we did have a party. It was Bob the Builder theme. Got him a big cake but bought him his own little cake. Then the day of his actual birthday we took him shopping. I think that's the part he liked best. He got to pick out two toys, one from mommy and one from daddy. Then asked him where he wanted to eat and we let him eat what ever he wanted to on that day(back when he used to eat real food, lol) then we let him pick his own birthday outfit. He had fun. The day of his birthday party we invited 5 kids his age(that was a mistake b/c they kept trying to take his toys and some parents just can't keep their kids in line)we let them run around the house. Then we let him help us w/the goodie bags. Just take like white paper bags and have him decorate them.
My in laws though were mad that we didn't have a "just family" only birthday party since it was his first!!!! I'll leave that one alone :-)
It'll be fun though...good luck.