There are Kid's clubs at several resorts, but they're all for children 12 and under. I can understand your fears. I've been waiting years to do the tour, and hope to do it this summer. I've stayed at AKL, and would feel safe leaving children your age there, but they would be upset if I went off to MK without them, and letting them roam the park alone would make me a little uneasy, but at least we'd be in the same place. Despite the horror stories, there are many members here who have been going to the parks alone or with friends since they were fairly young. Perhaps they will be along later to give you first hand advice.After all, Disney allows children 7 and over to come in alone...not that I would ever let MY 8 year old do it!
I think Now's idea of In-room sitter might be a plan.