I would generally avoid having 2 entrances to the bathroom. A pubescent child goes in, locks both doors, but only opens one when leaving...
As a concept for the house, I would provide an additional children's bathroom on the upper floor and make the master bathroom accessible only from the dressing room. So from the hallway into the dressing room and then either into the bedroom or bathroom. If children want to get to my bathtub through my dressing room, that doesn't bother me and guests don't have to go there.