I just think it's really hard to say nazly. Some women do do it.
My work is 100mph and physical and I don't really have any option to adapt it. If you were working from home, or at a desk, I'd imagine it would be very different.
Births are variable. I was walking about the same day but I had a completely straightforward labour; if you had a section or other complications you might be in bed for a week or so and getting back on your feet would take longer.
Women are very variable too. Some miss work and want to get right back into it, some really struggle on being away from their baby for the early months.
Babies are very variable too! Some sleep, some don't. Some are easy going and placid, some cry a lot more. Some only want their mum, some will go happily to anyone.
Breastfeeding exclusively would be difficult with a return to work at 3 months. Not impossible at all, people do it, but you would have to be very organised and research the hell out of getting a good pump, etc. You would need work to be accommodating of expressing (which they are required by law to do, but sometimes the reality doesn't match up). I think you would need good support to do this; friends who breastfed or a group you went to to encourage you.
I found breastfeeding tough emotionally returning to work at 10 months. Mostly the night shifts. (I stopped night feeds around 14 months).
I think getting the grannies on board is a brilliant idea no matter what you decide to do. The more people the better where newborns are concerned I think!! Is your partner taking any time off at all?
I do know some women who went back early and managed - they were in a bit of a daze I think, but they did.