Okay, I ended up really needing to do the shopping last night (we just moved into a new house, and the people who lived here took all the plugs, like for the bath and the kitchen sink, so I couldn't bathe the children until I went to Walmart and got one, and figured I might as well get the food at the same time...). So I ended up getting 5 Cokes, 1 Coke Zero, 1 Diet Coke, 1 Diet Sprite, 1 7-Up, 1 Dr. Pepper, and a tub of lemonade mix. All far too expensive as there was no sale, but I needed them this week and couldn't wait. I'm a little hesitant about coffee, as I don't drink it and I have no idea how to make it. It's possible, though, that there may be a coffee machine provided (it's at a sort of reception area at his work), so if there is, I'll see if my dad can make the coffee, as he drinks it.
The 4 square inch estimate was based on a 2" x 2" slice of cake. But even if it gets cut a bit larger, like 2" x 3", we should be okay. And that, of course, is assuming that everybody there gets a slice, and some people may not. I do think the idea of a salty snack makes sense, so I bought a couple of bags of pretzels. If there weren't so many people, I'd consider doing something like fruit as well, but fruit is way too expensive to make it reasonable to bring fruit for 50 people on top of everything else.
I bought a ton of ingredients for making all the cakes and cookies. Buying 10 2-liters is kind of crazy... my cart was crammed to overflowing! I did decide that you guys were right, and I wouldn't worry about the juice. So it's just gonna be soda, lemonade, and probably water (my husband says that there are pitchers and punch bowls and such there, so it's just a matter of putting some icewater in pitchers and mixing the lemonade into punch bowls--and our parents will be there so I will have help).
The other cookie ideas are fun, but I'm trying not to make this more complicated than I have to. I just moved into a new house less than a week ago and it's still a mess of boxes and such, so I haven't done any cooking yet. So I don't really want to try to make a lot of different cookies, especially with four little kids (one a baby) and the older ones wanting to "help" and driving me crazy. Oatmeal raisin cookies and chocolate chip are my specialties, and I can make both from scratch so they aren't too expensive, plus I figured they were different enough from each other. I agree that in general, adding maybe sugar cookies and peanut butter or some other kind of cookie would be great, I just can't handle that much work when I haven't even managed to find the box with my husband's shoes and I'm living out of a suitcase, you know? Plus then I'd worry that people would want to try one of each cookie, so I'd end up needing many more cookies than I've planned for.
I'm planning to make the cookies tomorrow and the cake Wednesday, as the event is on Thursday. Thank you so much everybody for your help in planning and figuring out numbers! Your ideas were great, especially like the idea of the salty snack and ditching one of the kinds of drinks to simplify things. If anything else comes to mind (that doesn't require me going to the store again--man, it's a long drive to the grocery store, especially when the GPS lies and thinks there's an exit where there isn't one...), let me know! And I'll let you know how it went.