Oh, I totally misread that, but your Mollies will be fine as well. The sizes are about the same. I would go with all females if you can, as breeding sounds interesting, but really ends up being a hassle later unless you're well equipped for it.
Mollies don't need salt if water conditions are kept very clean. I should have mentioned that. I overfilter and understock my tank with Mollies in freshwater and I have had no problems.