Re-introduce dad to mum and female baby after hes been neutered

Hi there, not posted before but need some advise! We had surprise baby Chinchillas nearly 4 weeks ago. We immediately moved mum and babies to a low flat cage, unfortunately mum got a bit freaked out and attacked one of the babies and it sadly died. We moved mum and the other baby back to the main cage and she was fine (dad was put in the low flat cage instead and he has been neutered). Baby girl is now 4 weeks old and doing well - question is, we would like to keep them all together again now that dad has been neutered but how do we go about reintrodung him as mum is quite skittish and I'm frightened that she may attack the other baby without thinking about it. We do have a new cage for them all (ferret nation 182 + 183 so plenty of room) that no ones been in yet as they can get quite territorial. Any help or advise would be great, thanks