Just to share my experience:
Once i had #1, we hired a helper and would ferry bb and helper to mil place every morning and back every evening after work. Did the same when #2 came along. But now with 3, I've taken a yr's no pay leave, so staying at home with bb and hlper while the girls go to school.
Reasons for taking leave: need more time with my children, supportive hb, tired of working. Also had enuff in CPF to cover a yr of housing loan, so I decided to try it out.
I still teach piano on my own time now, so during those afternoons when I'm out for like 5 hours, I'll send them to mil place. Also give bb some time to be in a different environment (won't jin chu "recognise house") and some time to bond with the grandparents. If you ship them off full day to your ils, just be careful that your helper is not overworked. Coz mine had to come back and do housework, sometimes till pretty late. Then I was a teacher, so she'd to go over early in the morning, meaning waking up early to do the laundry.
Maybe you can just have them go over 2x a wk or something?