You can pick up cheap 8" paper mache letters here USA only. This housed the cake, which I will provide a tutorial for soon. It worked perfectly. From Critters and Crayons. Party City also has disposable Spiderman paper cups.
quick links: superhero Party Supplies
If you don't want to get a kid's entertainer in, get a parent to dress up as a masked Superhero using a costume where the kid's can't see their face, below center and make an entrance halfway through the birthday party when they're least expecting it. Don't worry, it tastes of the fruit and not at all like spinach, so there shouldn't be any problems getting kids to drink it. Then use the Captain America shields from this ice cube tray supplier 3. Just Bunch has a pattern.