Gross motor skill update

We had a meeting with our son's PT and were told that his gross motor skills were almost at age appropriate level. Moreover, there doesn't seem to be any regress following periods of no therapy. That's great news, of course, but I still think he needs more strength in  his upper body. By the way, my son doesn't really like the balance disk. I love, and use, mine. I'm using this balancing disk. I actually feel the abdomen and lower back muscles working. Hopefully, we'll find a way to convince my son to use his. Anyway, for upper body strength, I've found a nice park featuring several types of monkey bars, and I take him there several times a week. He likes that a lot.