For example, if you have a nanny part-time, you will have to figure out nanny taxes - assuming you're doing it the legal way - or pay an outside party to manage the nanny's payroll.
That overhead may be easier to justify when the nanny is allowing you to work a full time high paying job, less so if the nanny is only coming a couple days a week. In this case, you might consider a part-time day care center instead.
And unless you have a lot of energy or hired/family help, you will be so tired in the first few years of your child's life that you likely won't have the energy to do anything beyond growing a few token tomatoes and potatoes, certainly nothing at the scale needed to make a dent in a family's food costs.
For clothing, tap your friends-with-kids network to get into the hand-me-down stream. Babies and toddlers grow out of clothes faster than they can wear them out, and new clothes are $$$.
Also, you mention you have a spouse. I know it is terribly unfashionable to say this, but have you considered being a single income family? Sounds like that would give you the best of both worlds.
In my case, we are a single-and-a-half income family. Once kids go to school, there's no much reason to keep an adult around home all day. I am officially the bread winner, and my wife has the lifestyle job, but considering how much she has accomplished just by working part time, we might need to revisit that decision sometime down the road.