This is a difficult problem you have encountered and one for which there is no definite answer. Indeed, the young are usually looked after by both male and female, unlike with the Syrian (or Golden) Hamster.

Because Dwarf hamsters are very social animals (again- unlike Syrian hamsters), they quickly become lonely when alone and are commonly kept in pairs. If breeding is not wanted, dwarf hamsters can be kept in same-sex pairs. Pairs are normally introduced when very young. The easy way to separate breeding pairs is therefore to keep a young female from the litter to keep the mother company and a young male for the father. Then separate the two pairs.

Now, I would recommend that you do try to reintroduce the male. I think it is unlikely that he would become cannibalistic. What I would be more worried about is the female rejecting him. However, this is just an opinion. Firstly, place quantities of his bedding around the cage to accustom the mother to his smell. After several days, place the male in the cage but be VERY vigilant.

Watch the pair for several hours. If their behavior seems to be normal, then they can be left unattended, but do check up on them every couple of hours. I would recommend that if there is any sign of trouble, then remove the male immediately. If reintroduction is not possible, reserve a young female to keep the mother company. I would recommend not trying to introduce another hamster to the father.