I started running with our GS last year. He LOVES it. I had the same problem with him weaving back and forth and I handled it like you said, tug on the leash no and constant reinforcement to "stay with me" which is our version of "heel" He also loves tracking work. We just play hide and seek with him. Your 8 year old can really get into the game with that one.... have him walk a weaving path through the yard around stuff.. etc. and then hide behind something. Then take your dog out and tell him to find him. My GS can track anyone in the family for miles through the woods. It is a lot of fun for him.