On our last trip, only one of my three kids was big enough for the coasters. For our upcoming trip, all three will be big enough for almost everything with 2 or 3 exceptions (RnR comes to mind). We're an odd number -- for rides like SDMT that only fit 2 per row, how will that work with our third? At the time of travel, they will be 8, 7 and 5. Can the 8 year old sit by herself directly in front of us? I think I've read that they can be 7 to ride alone in a ride seat, but I just am looking for some verification and some experiences from other families of 5.