We took our 7-year-old (in a double tube with me) through the canyon and had a blast. There is some paddling involved, so you aren't carried into the river bank or rocks, and occasionally you'd have to go left or right of an island. (There was also one part where you had to get out and walk your tube a super-short distance across the tracks to the other side of a bridge.) None of it was hard, but my kid would have to be older to handle this himself. Provo Canyon was gorgeous and it was equal parts super relaxing for us and adventurous for the kid.
The only negative was that we're in the height of COVID with cases skyrocketing, and no one was wearing a mask on the shuttle or in the shuttle parking area. The company website says masks are required, yet no one enforced or even requested this. That was sketchy and not at all cool--Utah County just hates science, I guess.