I know, I can't get my head around working afternoons either. I'm just thinking about a p/t job next year, my youngest is 2. I'd have to earn enough to pay for his pre-school for the first term as well as a CM to pick him up and feed him, luckily he'll have mornings.
My DD does afternoon pre-school now and actually I'd recommend it for a SAHM with a new baby. No morning rush and your LO might fall asleep in the pram on the walk there so you could even have a nap!
I spent this morning reading in bed while my 2 pottered and played upstairs!