i'm not an expert but i played junior b hockey while working out 3 days a week during the season..
on gamedays.. i would avoid doing any core or leg training... when playing hockey you use your core and legs the most... i generally avoided lifting ON gameday but if i did it would be an upper body workout. if you've lifted for a long time you don't feel sore after workouts anymore and it doesn't really affect you during a game.
when doing a leg/core workout, find a day in the week that will give you HOPEFULLY 2 days rest from games... you're legs will be dead for pracky and coach might get on u a bit but better than sh*tin the bed during a game, right?
i also found that i made minimal gains during the season (weights being lifted). i generally stayed the same weight during the season... most gains are made during the off-season for me.
i have a couple buddies that played high level canadian ball during their teens and they really focused on shoulder training.. maybe thats something you can do DURING the hockey season?