How old are your children? Personally, I would stop looking at it as what’s fair and focus on what’s gonna be best for small kids. Would your children feel better to be with their mom then with child care?
When someone gives up their career to take care of the kids, they don’t just give up salary - they give up experience and a 401k etc.
A way out of this for you, would be to offer her right of refusal. On your days, when you have to hire a babysitter - she can choose whether she wants to take them instead of having you hire a babysitter.
