Our entire family + 1 (mom, dad, 7 yr old, 9 yr old + extra 9 yr old) loved the move. The story is excellent on many levels. A smart girl learns that she does not need to act dumb to be liked. A nerd triumphs through adversity. A father and son bond. A pretty boy leans that he must earn respect. The animation is amazing. Plenty of action for the boys.
Up is surprisingly complex, intelligent and funny. The film includes unexpected layers and depth. My 6 and 8 year-old girls loved the humor and cheered for the endangered bird. I loved the characters and underlying story. This is not a fluffy, action-packed movie. Very young children will miss much of the story. If money is an issue, don't pay extra for 3D. If your kids can sit through a movie with good characters and sporadic action, then you and your children will have an excellent day with Up.
My husband and I took four girls to see HSM3. One six year old, two eight year olds, and one 13 year old. The girls all loved the show and the three younger girls were bouncing off the walls for 45 minutes after the movie ended. Stay for the bloopers - my girls quoted one all weekend. My husband loves going to adult movies, and didn't mind HSM3. I thought it was cute. Definitely worth the price of a ticket for girls in the 5-14 year range.