With Disney, I rarely think of them as big/little kid rides (except for the height issue). There are a couple of exceptions, but my 9 year old boy goes on practically everything. There is only one ride he hasn't been on yet by his own choice. (The theme of the Twilight Zone Tower of Terror was too much.)
Fantasyland attractions are fun, particularly the dark rides. The only kiddie rides (IMO) at DL are the roller coaster in Toon Town, Casey Jr. and maybe the Storybook ride & King Arthur Carrousel ( especially if an 11 yo thinks they are too old for this kind of stuff.) And Bugs Land in DCA. And even some of those are fun. The rest are really for all ages. I assume that both of the younger ones do not want or can't go on the coaster rides or Indiana Jones.
If you have fast passes for the coaster rides, you will be looking at about 20 minute wait for your son. Depending on how they are scheduled, it might be a good time to take a break in a shop or get a cool drink while you wait.
I don't know if this helps.