Is it ok to introduce two baby ferrets to my two 4 year old males?

That's perfectly fine! Introduce them in neutral territory where none of your ferrets go, perhaps the bathroom or a closet. The older males may drag the babies by the scruff of their necks, which is normal dominance behaviour. They will play rough for a while to make the babies know who is in charge and soon after should begin jumping and playing. Do not just put the babies in the older ferrets cage, they may become aggressive because that is their territory. You may have to keep your babies in a separate cage for a week or so but do place it next to the older ferrets cage so they can see and smell each other. Good luck!