Like some of the other obvious children of the 80's who have answered, I LOVE The Princess Bride and The Goonies and both are appropriate for 9-14 year olds (although Goonies has a couple of swear words in it and may be a tad frightening for some, but not traumatizing.) Other options are Annie, PeeWee's Big Adventure (cover their eyes during the "Large Marge" part, that did give me a couple of nightmares when I was 8) The Parent Trap (original if possible,) Willy Wonka and the Chocolate Factory (original ONLY, not that Tim Burton c****fest) The Journey of Natty Gann, and The Sandlot. If you want something more current, High School Musical is actually kind of cute and so popular, it's unreal, and of course, Shrek (in all of its incarnations) is fun for everyone.
Kind of random, but my 3 favorite movies when I was that age(none of which are kid movies, per se, although none of them are really "grown up" movies either) were Grease 2 (yes, 2...hehe.) Mr. Mom, and Max Dugan Returns. Aww, now I'm all nostalgic! *sigh*