Don't worry too much about aggression between females. In general, platies do not school/shoal. A 10 gallon is enough for just a few adult platies, not many really. You are correct that after 6 months or so you need not worry about prior male contacts.
I am at a loss. What is it that you want to teach your children? If you want them to observe fish mating and reproducing, you have set things up to avoid that outcome. If you want them to see females deprived of male company, it will be a long time before they can see that. If you want them to see anything related to genetics and inheritance, you have missed that chance by refusing to acknowledge the male's role in things. I am not stupid by most accounts, but I cannot see where you are going so far.