I would have to say let her stay with your MIL. We took our boys who were 3 and 11, and I felt sorry for my 11 yr. old most of the trip because he was held back in autograph lines or kiddie type rides, if not then it was because we had to split up, which wasn't fun either. On the up side, we are going this year, and the boys are 8 and 16, a much better combo, I'm very excited about riding everything together, and staying together more!