I work in the public service so have pretty good "family friendly" conditions, at least for the first two years... so not sure if what I have experienced will be possible for you, but..
I took 12 months off, then returned for just 2 days a week for the first 5 months. My
DH (also public service) dropped down to 4 days a week so
DD was just in care for one day initially (and this was with a mum's group friend, we swapped kids once a week!) Then I upped it to 3 days a week (started daycare too) - partly for financial reasons, but also because my boss was happier for me to work 3 days and would be more likely to extend the part-time arrangement beyond the "compulsory" two year period if I compromised early on and did 3 days. I can definitely see his point of view, 3 days a week is a lot more productive than 2, and I really "own" the position (have someone else job-sharing for 2 days a week). I feel exhausted by the end of the third day, its tiring, but professionally I think its the right thing to have done and I get a lot of job satisfaction out of it. I LOVE my Thursday's and Fri's at home, truly, I appreciate them so much more. Financially three days a week is pretty good - I am still in a low tax bracket so I don't earn that much less than 5 days. I have been fortunate to have a pretty flexible system. My
DH has just lost his job (contract ran out and isn't being renewed

So, we will be struggling for a while until he finds something else, but we can scrape by on the essentials with my 3 day wage, just! I wouldn't want to work full time again, I would rather be poor!!! I reckon go with 3 days from the start, if you can!
Sorry for long winded reply... !