My family is a nice healthy mix of alcoholic dysfunction with a sprinkling of depression thrown in. 3 out of 4 of my grandparents were alchies, my mom is recovering, and my Dad is still active. I'm recovering and in my 5th year without alcohol. My sis suffers from PPD and had an entire year in high school where she was in bed with depression. We all have anger and control issues. That being said.....
Yes, this stuff us most certainly genetic, but it's hard to tell if alot of it is "emotionally genetic" I just made that term up myself but what I'm trying to say is that I think to a certain degree there are hard-wired components, but also that those components can be triggered by dysfunction in the family or even by environmental factors. My son is ADHD and dyslexic, the product of me and another alchy who is happy that way and I'm no longer with. I have had success helping with his symptoms by eliminating as much chemical pollution as possible (within reason....if you tried to do it 100% you would have to lock yourself in a porclean house), and supplements. He is a very happy kid and brings me much joy! I don't doubt that he will have issues that come up throughout life that will trigger some dark moments, and I hope and pray every day that he won't see life reach as dark a corner that I found myself in before recovery, but I just have to have faith that he will be capable of overcoming the obstacle that are thrown in front of him...not just in spite of, but sometimes because of his differences. Hope this makes sense and gives you some insight.
I think it would be a shame for you to deprive yourself of such a wonderful gift as parenthood...but I can also relate to your reservations.