As a mother of 3,(raised 4) I cloth diapered all of them from the time they were born until they were potty trained. Used the same 6 dozen flat unfolded flanellette diapers, with the old fashioned plastic pants and diaper pins
They were cheap, long lasting, easy to wash and I air dried them (in a heated basement , under a vent, in the winter) and outside in the summer.
You will save a lot of money there. We only used disposables when away from home.
Don't worry about potty training the 2 year old too soon, if the child doesn't seem ready. It will only stress you and the child.
Babysitting another newborn plus your own, and a toddler is plenty of work.
Your wife doesn't need any more, so as 'to earn her keep'.
If she decides to quit work until the youngest goes back to school..or forever, you should support that decision too.
With the cost of daycare, work clothes, and food, you will probably not make any more income than if she continues to stay home and looked babysat one other child.
$600 is a lot of money for groceries. This could be easily reduced to $400 month (or even lower)
Don't be in such a hurry to retire, or forget what is really important....family.
We almost always had one parent at home, while the kids were growing up.
When they were small, I also babysat in our home.(3-5 extra, some days) If I had it to over again, I probably would have found other ways to reduce costs. It was very stressful babysitting and having 2 preschoolers.
We still ended up retiring at 46 & 50...when the youngest finished high school.