Way out of bounds. Either have a mitzva tanz, or don’t. From what I’ve seen lately, the kallah coming over to the mens side for ketzad merakdim has been eliminated, as a sign of yerida ha’doros.
The mitzva tanz is after the meal, when most non-family members are gone. And, the few mitzva tanzs I’ve been to where the married brothers get called up, they hold a gartel, not hold hands.
And bochurim? I had my head handed to me by my rov when I sent up my 6 year old to dance with his aunt (my sister). The rov said this is no place for bochurim.