My husband and I went to the Studios over Memorial Day weekend. Naturally, it was fairly crowded and we were able to get on Toy Story Mania shortly after we arrived (that's a whole different story). Anyway, we thought the family of a father and his two sons and one daughter in front of us were with an older couple in front of them. They weren't and the two older people went to the separate way for parties of two. Neither my husband nor I thought about the father and his three young kids in front of us until we reached the seater. The father was asked how many and he replied "four". Then the Cast Member asked how old the kids were and they told him. All were under the age of seven. The father was told that the Cast Member was sorry but they wouldn't be able to ride. I was going to speak up but my husband did it first. So, I rode with the little girl, my husband rode with the oldest son, and the dad rode with the youngest son.
So, Disney can be strict on the ages of the kids. And, there is some leeway as well as the Cast Member looked relieved when we offered to help.