My wife and I waited 'til we were both 30 to have kids (we had been married since we were 24). Because we waited, we decided that we'd go all in when we did have kids--one of us would be at home with the kids, and likely homeschool (which we are doing). We made the commitment to change our lives in order to be parents. We weren't going to shoehorn kids into our lifestyle.
Additionally, be ready to sacrifice your time for your partner/spouse's sake, especially during infancy. Both parents need some time away, particularly if one is at home with the child. Early on, I considered my time at work my "free time," and was willing to give up trips to the climbing gym in the evenings so that my wife could get out of the house. As I said, this is only temporary, and as your kids get older, it's easier to share what you love with them (that's why we've never stopped climbing since we had kids--we can easily do it together, and the many road trips have provided lots of bonding experiences).
Another thing I've come to realize is that raising your children really is a way to make a positive contribution to the world. The work you do as a parent is profoundly important, more so than any hacking project or start-up. You will have time for your own big ideas again, so don't waste the opportunity you have with your kids.