A lot of the kid!fic i've found is Clint and/or Natasha (or the whole team) being turned into kids by magic or what have you (although I found a high school AU) and the problem with that for me is that it's assumed that there's a load of bad things that have happened to them as adults that they've forgotten and bad stuff when they were kids that's now revealed, which whilst cute and moving means at the back of my mind there's always the fact that there's no potential or possibilities for them - the future is fixed. I'd love to see a kid AU so that I don't know what the future is going to be for them and that the author could make it be an alternate or same Avengers type future or something completely different and I'll be full of hopeful feels for them. Even if those hopes are dashed *grins*.