I've music directed quite a few of the MTI Jr shows. Aladdin, Little Mermaid, Honk, Seussical, and Shrek are all solid adaptations. Beauty and the Beast is too long and does nothing to simplify Beast or Belle's harder solo songs for younger voices. Same with Music Man and Into the Woods--the material is still very challenging for the age group's intended. Mulan's only advantage is a huge cast. Lion King is basically a staged concert in the Kids or Jr version.
I haven't worked on them yet (soon, hopefully), but Alice in Wonderland (now a JR version instead of a 30-minute Kids version), The Phantom Tollbooth, Freckleface Strawberry, and James and the Giant Peach all look like solid shows on paper.
Basically, these shows are only as good as the adaptations. It's not enough to just cut out lines and verses and say it's for children. I had to tinker around, for example, with quite a few of Ariel's higher phrases because they expected a young child to pop out some random High G's in the middle of otherwise altered phrases. The scripts are usually in better shape the scores.
I'm trying to get some people I know to test out the G2K Rodgers & Hammerstein shows. I think those classics, especially Cinderella and Once Upon a Mattress, could be well-suited for younger actors. Theatrical Rights Worldwide has some promising Young@Part editions of newer shows like Addams Family and All Shook Up; they have Curtains and Spamalot, too, but I question how those could be made content appropriate for younger performers.