If finally wants to see his girls!?

I would certainly suggest a group of people be with him while he meets his daughters, but I also 100% think he SHOULD and has every right to meet them! It makes me happy to know he wants a part - even a minuscule part - in his daughters' lives. However, his bad habits aren't healthy for babies and to prevent arguing, you should have his mother there, you there and maybe even your mother there. It also is wonderful to know that you and his mother get along so well - that must be very helpful for you. Good luck!