I think you could use Manage Sims to delete the unwanted pets and babies but I've never tried it. Good luck with whatever you decide to do.
That works for pets and adopted kids, but the game doesn't let you delete infants through Manage Households. You need to have a sim physically go to the lot with the infants on it and use a cheat to delete them.
Sometimes I got infants from expand the family question. I just moved all infants via household management to a townie and then delete the household. No need to aging up these infants or play this household. // Not all cheats are access bar in a vanilla game or for console, and I think this cheat is one of this. You need a mod for full access to all cheats as destroy objects etc.
