QoQ, I'm really lazy, but I still help out at kid's parties. Not generally with the food, but with the child wrangling.
My current grumble is, I always stay for other kids' parties, as I generally have DS2 as well, who enjoys the party but needs supervision (and is too young to expect a party bag etc, so he's not straining the planned resources, IYSWIM). But then I end up just eating leftover fairy cakes!
Realistically, at the 3-4 year mark, parents holding parties are dependant on having some parents stay and help (which I'm happy to do), but they could feed us!
Oooh, and at the last one, I went off to the loo with DS1 and one of his friends (there without parents), and asked a friend to mind DS2. When I came back from the loo, everyone had left the soft play area, leaving DS2 behind! He's only 11m, and thankfully wasn't bothered, but I was extremely pissed off.