I just went through this same scenario last summer with my own baby #2. I ended up keeping my older child (she turned 3 right after the baby was born) in daycare. I talked to her "teacher" before I had the second baby, asking her what most parents do. She said it varies but she's seen the best results with older siblings who stick to their routine. It's a huge change to get a sibling in the first place. And then if you take them out of their daily routine immediately after it happens, only to return back to daycare when you return to work (in my case, 12 weeks later), it typically confuses most kids (per this certified teacher who cares for 2-3 year olds and has done so for 20 years) and they have a really hard time with the transitions.
It ended up working very well for my daughter and, most days, she preferred going to "school". When I did keep her home, I think she got bored since I couldn't play with her as she's used to playing at school. She did ask one time why her baby brother stayed home and she went to school (it was more of a general question rather than complaining about the difference) and I just explained to her that he was too young and wasn't allowed to go to school yet which is why I had to stay home with him. I explained that I did the same thing with her when she was born. I also explained that he would be going to school when he turned 3 months old and that I was hoping she could show him to his room (the infant room is just down the hall from her classroom) and tell him all the rules. She seemed to like that idea. That was (and still is) my key to helping her feel included. I tell her stories about how she was when she was her brother's age and ask her if she thinks he's the same or different. It opens lines of communication and helps her to see that she was once "the baby" too whenever she may be feeling like we paid too much attention to our newborn.
My best advice is to go with your gut - you are the only one who knows how both you and your older child will react. And you need to do what is best for both of you, based on that knowledge.