I had both kids home with me but I had either my mom or MIL on call to take the big one for the first few weeks when my husband was at work
I’m keeping my son in for 2 days when I have our second baby. It means a) he can lots of attention with his key workers and play with his friends, he will get outside lots too and have loads of stimulation which if I’m having a rough day he might not get. B) it means baby gets all my attentions for those two days. I think toddlers thrive off routine.
We kept our eldest at nursery for his normal 4 days but if money had been an issue we'd have cut down the days. It was so nice to be able to have 1:1 time with the newborn like his big brother had with me.
My oldest 22 months is starting 2 days a week in Nov. Baby sis is 3 weeks old, if you can afford it definitely have a couple days in day care
If you could do daycare part time or once twice a week then I would so the transition is less stressful with 2 under 2