I agree with the previous post that a 10-year old (and even his parent) might really enjoy downtown L.A. Everytime someone writes, "there's nothing in downtown L.A. to do," I wonder how much time they've spent there?

Yes the architecture is really interesting and varied, from early 20th century to very contemporary. A short walk from the Bradbury building on Broadway through Grand Central Market and up to California Plaza will take in quite a lot of it.

There is a small but very vibrant Chinatown. Also Little Tokyo. Olvera Street, where the city began and now an "Old Mexico" shopping area, is very touristy, but for a reason. All of these places are safe to explore on foot.

There's also the Central Library, the giant wholesale flower market, the Museum of Neon Art (very cool!)... well, how much time do you have??

(and just to clarify, I'm not saying don't see anything outside of downtown, only that there is much to see and do there).