I am married and an entrepreneur for the last two years. My wife and I have been putting away expanding the family thing for while, basically waiting for our startup to reach either profitability or a level of funding where I could draw a salary.
How did you guys manage the expenses? Were you drawing a salary or had sufficient revenues to support yourself when your wife was off work/due?
It's much easier to have kids when you are young, and as long as you have prospects for income you'll be fine. If you wait till after you are perfectly set it will be too late.
Realistically - if your startup failed, could you get a job? If yes, then there is no need to wait, you are set for money.
So if you and your wife manage now, you'll manage then just fine.
3 children later, it's 8.5 hours on weekdays only. It changed my working practises so that the moment I sit down at the computer it's the top priority task right now and everybody be damned until I need my first long break.
I also find myself asking the question when someone is looking for free help/products "do I want to spend time helping this stranger or spend time with my children?" It focuses my attention on the money, but makes you kinda selfish towards your family, in that regard.