UM,
My DS isn't into anything like this and we have to drag him to physical activities and insist on them or else he would be a puddle of goo on the floor, but, we live in a chess intensive area and have seen much. I would second Colin's mum, and your own instinct here about it being fun for him - my DS had a brilliant chess kid in his K class, older brother played and the trips to nationals and regionals were big family outings. The kid hated it - he was brilliant at it - but hated it - the kid is no longer at DS's school - but his brother, who got much less attention for his chess, is still doing quite well and placing statewide - the younger is nowhere to be found. Refusing to play, throwing fits. So I would say that his interest and willingness to be coached is a good sign of passion. Now, you still have to balance allocations of family resources, family time, and physically activity. But I think you are on the good side of things focusing on happiness, so long as nothing else is being dropped.

DeHe