Honestly, it's a myth that being an entrepreneur is the exclusive domain of the young. People in their sixties have successfully founded companies. Never let anyone tell you you're too old.

Having children, on the other hand... it would be great if the same were true there, but unfortunately biology dictates otherwise; this really might be your last chance for that. Besides it seems like this is also the time when your wife needs a break from the office grind. Maybe she'd feel like getting back to that in later years when children are grown up.

So to be honest, it sounds to me like she's right, this is the best time to have children, and think about the startup game at a later date.