B.M.
Personally, I went back part-time but working fulls days b/c that's what works for us. The days I worked were long days, but it ultimately meant I was spending more time with my kids.
Here are my suggestions for you to think about what your preferences are:
1. Time spent packing and shuttling daily vs. 3 days/week
2. Cost of daily care vs. 3 days/week.
3. Cost of gas, parking, and lunch daily vs. 3 days/week.
4. Nature of your work (is it time sensitive) and the attitude of you boss and co-workers about adhering to your schedule. If you're there daily, is it likely you'll end up working a little late each day b/c of last minute requests b/f you leave?
5. If breastfeeding, does your work have a room you can use(other than sitting on a toilet in the bathroom).
6. You and your babies emotional needs. Do you need to snuggle mid-day? Do you need the adult inaction daily?
No matter what schedule you decide to start with, nothing is set in stone so if it's not working then try something else b/c it's so hard to know what will work until you try it. Good luck!