I have held back as my experience is outside of the Rail industry but as it seems quiet, here goes.
I spent the first ten years of marriage working away from home for weeks on end, followed by fifteen years of shift work, usually a mixture of days and nights.
The key for us was that we were both completely happy with the work/home life balance. If you are both content with the situation then nothing life throws at you will be insurmountable. I am blessed with a very, very understanding wife who has put up with more than I had any right to expect and this is what has made our lifestyle work.
Believe me, work patterns are only a half of the challenges. There will be plenty of other events to sort. For example, having phoned home after a couple of weeks away, I discovered our neighbours had been burgled and completely cleaned out. Was Mrs X phased, not a bit of it, she reckoned the presence of several coppers made her feel safer than normal. On another occasion, Mrs X was rushed to hospital whilst I was away. Somehow we coped, with the help of family and friends.
A positive attitude and your determination to make it work are your main weapons. Talk through all the possibilities and develop coping strategies to cover what you can predict as problem areas and you will be halfway there.
I can honestly say we only had one slight wobble in thirty years. I was coming home after a couple of months away and I had phoned home to say I was an hour out. My boss then phoned us to divert us away for another few weeks, before I got home. I told him I had just called home and he said he would call all our wives to sort it. When I finally got home a couple of weeks later Mrs X was fine about it. I never found out what my boss said to her and I never asked.
Good luck and congratulations on the new arrival. Hopefully others in the industry will be able to help on the finer points of Rail shift working.