I would be a bit concerned about the onset of a mood disorder as well (this is the prime age for that), especially where you are describing a history of emotional lability which tapered in latency age, and now is starting up again in early adolescence.
At the same time, I have a very exuberant child as well, who, although effervescently happy the vast majority of the time, is very clearly triggered to irrational tears by fatigue, hunger, and illness--any kind of physical discomfort. Have you tried an afternoon nap before games?
