what's wrong with boys to love jazz dance (or dance in general)? have you watched 舞動全城, being able to dance is a very joyful thing. just take a look at aaron kwok, does your husband (or grandpa) think aaron kwok is girly?
you can try my son's dancing school. They have hip hop class today Sat 3-4pm at Prince Edward(just above the MTR). We have 4 boys in our class. As I know there are 8 boys at the other branch Tokwawan. Any interest, pm me.
Well, I am glad you have a son with independent thinking; he just asks for what he wants. BTW, why don't you trade with him on his after school activities, e.g. maintain good result etc; Win Win situation.