Congratulations on your new betta babies
At this point in the fry's development the father fish will be very busy making sure no fry fall out of the bubble nest, when a fry falls he will catch it in his mouth and put it back up into the nest, the first few times he does this you will be very convinced he is eating his fry(he might be) but usually he will spit the fry back up into the bubble nest...he shouldn't be eating them, though a few might get swallowed by accident. Of course if you do notice that all of your fry are disappearing down his throat one by one then I would remove him, other wise you should leave him in until the fry are free swimming...more often than not he will be a good daddy and his presence there will only increase there chances of survival.