I don't think any of the character meals are really geared toward young children. there are always plents of adults only that go to them too. The characters might just act differently with young children than they do with older kids or adults.
That being said, i think that any characters that your kids particularily like would make a great meal to go to. If they like mickey there is chef mickeys, garden grill, etc. We really like Crystal Palace. My 14 year old still has a fondness for pooh and friends. I think if you ask your kids and make them part of the planning process they will probably end up enjoying it more. You can look at the menus and see which characters are there.
Whatever you choose, have a wonderful trip!