M.K.
My son 8 and daughter 3 share a room - the only thing I have tried to do, is give them a little space of their own - my son has a loft bed, and little sis is not allowed up there, that is his space - the girl doesnt care at the moment about her own space.
once they indicate that they want their own room, we will have to build on - but at the moment they are happy to share.
dressing is no problem, I dress my daughter, as she cant dress herself yet, and my son likes to dress in the living room, and puts a blanket over his nether regions while dressing.