Good job dad!
My daughter started riding our ranch horses when she was 4 years old. I told her from the beginning that if you ride horses long enough you're eventually going to fall off or get bucked or drug off. When it happened to her the first time due to a busted latigo, it didn't scare her near as much as it might have if I hadn't pre-warned her.
I believe riding horses really helps kids' muscle memory, flexibility, and balance, which pays off later on if they're athletically inclined.