I would assume that it would be fine.
However, it would be more difficult to track the breeding between the 3 snakes, IMO. I think that if you put one male in, and you only saw locks with one of the females, you may have a better chance of getting the other female to lock if you put them together alone.
Like, one female would be neglected more often than the other, and one may not produce while the other one does. It just seems more risky to me by giving him one choice instead of 2 each time if he ends up going to the same one each and every time.