My son is 5 now. He wrestles on our elem. team. I coach the 4, 5 and 6 year olds on our team. I find that he is not as motivated to practice when I am there, but he practices pretty good when I can't be there for whatever reason. I think it is difficult for him to understand that I have 16 or 17 other kids that need my attention also. It seems he is always trying to get my attention away from the other kids. He is doing better this year than he did last year, but it still happens.
The hardest thing for me is balancing the coaching with the parenting. I have to know when to coach him after a loss and when to shut it off and console him as a parent. I get more frustrated with him since he is my son than I do with the other kids, but I am learning to treat him the same as everyone else when we are on the mat. It is a learning process for us both.