Bobbi Pavis, Barbara Horan, Jeana Loring, etc - The Malibu Bikini Shop (1985)
The video store around the block from my house rented this to me as a 4'th grader.
There were more scenes than this, there were a couple more parts where the one brother got to keep watching a lot of them changing through a two way mirror. One part lead to a fat chick and he was grossed out. lol
I didn't know then it was going to be a voyeur tit video. It was a funny cheesy 80s movie all the same though.
None of the links I post are mine.