I know Cannon/Mittersil very well. Its a great place ...when there is snow. Cannon is also
probably one of the harshest condition mountians in the North East. I'm sure you know but
they have a great kid area that is tucked off the side of the hill with its own little lift protected
from the wind.
Good thing about Cannon is your not far from other hills as well. 1 hour to the river. 1 hour to Jay. 45 min to WildCat etc. Bretton woods would be good for the kiddo as well. Very tame. I would choose the River going by current conditions though.
Family friend has a Chalet right on Mittersil. I always feel i'm in the swiss alps when in that village. Love it there. Loved it more before they put the lift in.