Gamer Moms and Dads, I Feel Your Pain
I recently read this great post by user Menel4us recalling his past gaming exploits and lamenting his loss of gaming time after the birth of his son. Being that I'm a father of two (a nine-year-old and a 21-month-old), I thought that rather than spamming the comments section of his article, I could write my own "user guide" for how to deal with your gaming hobby when your family of two gets bigger.
First of all, there will be dark times for your gaming immediately leading up to the birth of your child and for months later. Your wife will need more attention leading up to the birth. I would absolutely NOT take this as time to "get all your gaming time in" before your kid is there. You're going to want a pretty tight bond with your wife, because your relationship will definitely be strained when you're both going on hours of sleep a week.
For the first couple weeks after birth, you will likely be on a bit of a high and may or may not feel tired. This will almost definitely pass, especially after you start working again. I would highly recommend going to sleep when your baby does, and not taking the hours from 7 to 11 to catch up on your gaming. The temptation will certainly be there, but the issue is, most kids are up A TON during the night. I would go to bed at 7 and get up at 6 to get ready for work and still feel like a zombie. I can't stress this enough: YOU WILL BASICALLY NOT PLAY ANY GAMES FOR MONTHS. Sleep when you get the chance, seriously.
Now this will definitely get better over time, but it is really gradual. Our second didn't sleep through the night until about 13 months (this is atypical, but happens). Once they make that switch, things get significantly better. You can stay up a bit later, and not have to worry about being slackjawed the following day. I will say, that once you have kids, your daytime gaming will basically stop; especially as they get older (at least, M-rated daytime gaming will stop).
Now this sounds very doom-and-gloom up to this point, and I realize that. Now, there are some really great things about having kids as well. My nine-year-old and I have recently been playing a good bit of Minecraft and Kerbal Space Program together during waking hours. These are games I would have never thought to try on my own, and we've had great experiences in each. The Traveler's Tales Lego games are also mostly great; though after you've played a few, you've played them all.
There are also tons of non-gaming things that kids enable. My older son and I have spent many days at a college several blocks from our house stalking college students and trying not to be spotted. Needless to say, this is something a normal 31-year-old might get arrested for if it weren't for a nine-year-old companion (it is also REALLY fun).
To summarize, kids change basically everything about your life, mostly for the better. Don't expect to continue living the way you were before kids, or you will be sorely disappointed. The trick is to embrace the things that you can do with your kids and be OK with losing (or limiting) some of the things you can't.