Good point. Can you share some?
Then when you're sick of it, move to a cheaper area, get a part-time job and sell 3-4% of your assets every year to make up for the deficit. If you're lucky, the safe withdrawal rate of 3-4% will even be enough (or close) to have the ability to quit working for a living completely. Or perhaps your part-time job can cover all your expenses and you can just keep letting your portfolio grow at the expected long-term rate of 6-7% per year.
But obviously, your total spending will increase, so you either have to earn more after having kids or save up more before having kids. If you want to raise your children in a high cost-of-living area, this will of course be even more pronounced.