My kids are also so into anime. They started with Pokemon, which really is far more than the TV show; the Pokemon fantasy world of the Game Boy games is complex and involves math and logic skills, implores kindness and consideration, and is so multifaceted that if your seven year old does not have one of those games, you should run to buy one for him.
Anime is THE big thing for smart kids, usually males, to enjoy these days, and as long as it's G-rated, it celebrates intelligence, is creative, and is not as formulaic in plot as the boring American fare like Scooby Doo.
Spirited Away is lovely. I cannot wait to see Miyazaki's latest, "Howl's Moving Castle", which is based on a novel by Dianna Wynn Jones, an English fantasist.
How old are your kids? Are they ready to move on from Pokemon? I "induct" my younger siblings into anime as they enter their teens. Usually start them with something fun, but meaningful and telling, like "Rurouni Kenshin".
Yes, I love Spirited Away, and it did win the Oscar last year, beating a couple of blockbusters in Lilo & Stitch and Ice Age. Sort of an upset.
And while there's a lot of anime you would never want to show kids, there's still a lot that's great for kids, and a lot that's not at all childish. Hayao Miyazaki's films (Princess Mononoke, which is rather violent, being an exception) are an example of intelligent stuff that kids can enjoy, but are great stories that anyone can like. Maybe a few are a bit intense or complex for a seven year old, but I Kiki's Delivery Service is a terrific film, one that my younger siblings saw before even I did.