I'd separate the father from the mum and babies. If you don't have another tank, you could try a glass divider.
It's been ages since I kept fish, but I vaguely remember having to do this before.
You can buy nursery nets at most aquatic centres. Its a box shaped net, that clips over the rim of the tank and sits in the water. Mum and babies can swim around in there safe from the other fish, without having to be removed from the tank.