DD is 9 and we have done single rider for RSR since DD was 8. One day on our trip this summer we did it over and over and over. I bet we rode RSR at least 5 or 6 times that day because it is her favorite. We have not had any issues. She knows that if she gets off first, then she is to stay in the photo area until DH or I get there. She knows that there is a chance the ride could have issues and that if we are off first we wait, and if she is off first, she stays put. We typically have me in line first, her second, and DH after her, but depending on where they place you when they pull you out, that does not guarantee that I will get off ahead of her. She could get pulled for a spot for a ride cycle ahead of where they put me to wait. The only time I ever had any concern is when she was 8 and my car was diverted to the disabled boarding area for exit in a line of cars to pick up some groups waiting. That time she was ahead of me and I saw her car go to the regular unboarding area, while mine was diverted and I had to wait in the line while at least one car ahead of me boarded something that with difficulties that took a while to get loaded. I knew DH had not made our ride cycle. At the disabled entrance the CM was directing me to exit a different direction which would not take me to the photo area (basically out the disabled entrance I think). When I explained that my young DD would be waiting in the photo area, she re-directed and sent me that direction. It was fine- she knew to stay put and was not remotely worried. She knew one of us would show up. She loves it, especially if there are kids in the row where she gets placed. I would not have any issue sending a 9 year old, you just need to explain what to do for delays and where to wait for you and not to move from that spot.