For me personally I would watch one piece with them since thats a classic and got me into anime.~
assuming that when we say "kids," we are not talking about teenagers, i would show them naruto. it was my first anime and i was like... eleven years old? naruto, for me, is a show that is easy to understand so i had a lot of fun watching it.
if i showed my kids something like steins;gate... they'd probably fall asleep because it's sort of (really) complicated and hard to understand what's happening... even i had trouble understanding (i hope it's not just me) it and i had to rewatch to really process everything :'D
if possible, i'd get them to read bleach (not watch... the anime sucks), but i feel like they might not like reading manga until they are teenagers?
anyways, i'm rambling XD short answer is: naruto :P
Saint Seiya The Lost Canvas Meiou Shinwa
this so they can suffer with me due to the lack of a proper ending to the anime
I'd probably start with My Neighbor Totoro, Kiki's Delivery Service, and Ponyo, maybe Howl's Moving Castle also, and wait until they're just a little older for Nausicaä of the Valley of the Wind, Castle in the Sky, and Spirited Away. While Akira is my favorite, they likely wouldn't see it until their teenage years.
I'm surprised by the lack of Studio Ghibli representation in the replies. I'd definitely consider myself to be a newbie/non-committal anime watcher relatively-speaking (see my profile for proof), but Totoro, Kiki's Delivery Service, and other Miyazaki films would be my go-to picks, 100%. Those were the anime that started it all for me, and they are films that even non-anime-watchers tend to appreciate, making them a perfect segway into the anime world.
I haven’t seen any but some look like great movies a kid would enjoy
Yeah, Studio Ghibli makes some great stuff for all ages. Kids are able to enjoy the films for the storytelling, but older folk can appreciate them as well and pick up on many more of the subtler messages thrown into each film (trying my best not to sound too childish myself, haha). Classics for sure.