With that general structure in mind, I made a super-computer cake with a cardstock screen that I wrote the "problem" on: "Natalie is 4 today, What Should we do? _ _ _ _ _ !"
To start off I had the kids color and draw pictures of themselves as Super Heroes while all the guests arrived. In attendance were our cousin Evie (and her mom and little sis & baby brother), a friend from our old ward, Carissa, and the little boys Natalie plays with when I go up to the school, Joseph and Ethan (and their mom). Michael and Emily weren't officially guests, but they were my super-helpers, guiding the younger kids through the games.
Our first game was an alphabet treasure hunt. I hid prizes around the room, stuck letters near the hiding places, then had the kids draw letters from a hat and match them up to find the treats.
Then we played a letter "bingo" game. I made 9-square grid cards with various common letters and bought some cute party favors for tokens. Instead of saying the name of the letter for them to cover, I showed a picture and had them decide what sound/letter the word started with... It went pretty well!
By then we had discovered our five "super letters": P-A-R-T-Y
That meant time for presents and cake!
Here's a collage of the festivities:
All in all, I think it was a success. The cake turned out ok, the games held the kids attention and we wrapped it all up in two hours. Guests went home with a small bag of candy, a set of magnetic letters, and a copy of the "bingo" game board and tokens. (Hopefully the parents won't silently curse me for the number of small pieces this ended up being!)