This is not your last chance to so something entrepreneurial, but it is getting close to her last chance to start a family. (And quite frankly, for every year you continue to delay having kids, the physical stress of raising them is going to get that much more difficult. Much easier to handle a toddler at 30 than it would be at 35 or 40.) Your wife's desire to have children is not a hobby or an affectation, it's the human condition. Do what's best for your wife and children, and you'll be rewarded many times over.

As a bonus, you will quickly develop the ability to survive on far fewer hours of sleep per day. That'll come in handy when you're starting new ventures in the future...