Hi, I'm normally just a lurker here but just had to respond to your post.
I had a mastectomy age 24 and went on to have 2 babies. With the first one I went through a terrible time trying to breastfeed - I managed 10 days but had to stop after that. The thing that I found most difficult was the memories that resurfaced of the op and treatments. When my milk came in I could obviously only feel one side - the one breast went massive and painful and I found it very difficult having to think about my boobs and look at them all the time (if that makes any sense!) It brought back a lot of feelings I thought I had forgotten.
Of course, things may be very different for your wife, it is certainly physically possible to do it and she may take to it beautifully. But I think what I want to say is that I was never prepared for the emotional side of things and the memories that resurfaced very vividly. Of course I don't know anything about your wife's history but just wanted to advise that this could be an issue.
My very heartfelt advice would be to take each day is it comes, don't put any expectations on yourselves. The most important thing to your baby is that their mum is happy. If she has to use formula to achieve that she must not give herself a hard time.
I put myself though a difficult time, and a massive guilt trip trying to make breastfeeding work with my first. With my second (now 9 months) I decided not to do that and that every breastfeed would be a bonus but not something I would expect fron myself. I was thrilled with 3 very special breastfeeds with him, but I'm afraid that I felt unable to continue after that.
I really don't want to put you off and I really hope your wife is successful at breast feeding. My difficult experience certainly doesn't mean that hers will be. But I think I just wanted to prepare you for possible emotional issues (as well as the physical challenges that the breast advisors will be able to help you with). Every single breast feed will be a massive achievement after what she has been through and she will need all your love and support.
It is pretty uncommon to meet other women who have had pregnancy after mastectomy (I guess partly because pre-menopausal breast cancer is rarer and partly because of being the high chance of sterility after chemo) so if either of you want to chat I would be only too happy to help if I can. Please just shout!
Many congratulations on the pregnancy and I think you are fantastic for being so well prepared and supportive. I wish you every happiness.