I think pizza would be just fine. No one will mind if it's a few minutes late, and if it comes early you can warm it in the oven. I think pizza is probably the safest choice for kids. Personally, I think the crazy long party subs from subway are fun for parties (you know, the ones that are like 4 feet long and sliced up), but they may not be as big of a hit for that age group of kids. I've been to some kids parties lately that had nice party trays from Chic-fil-A (not sure if you're ok with buying from them or not), and they went over well with both kids and moms. Really, pizza is probably the simplest option. The kids will be to excited about seeing each other to sit down and eat right away anyway, so I wouldn't sweat it if the pizza arrives late.
Mom to J 6/25/08 and M 6/21/11