D.B.
Are the two locations close enough together that you could take them to separate places for awhile? That's a hard choice to make...I'll just feel you in on my experience to give a some insight since there's no easy answer...
Both of my children went to an in-home daycare from the time they were about 9 weeks old until last Fall (they were 3 and 4). First, let me start by saying I can't say enough good things about our provider (maybe she was a bit eccentric and opinionated, but she did put up with me and my "by the book" attitude as a first time mom, what a change when it comes to the 2nd child!!!). She provided lots of love and a place for them to feel secure...she was their second mom (if you really think about it, with me and my husband working full-time, she spent more time with them during the day than we did!) While the larger centers offer many things for infants, I'm glad I went the in-home route because I feel they were given more attention than they would have gotten at a large center. That being said, there came a point where I felt they needed to move on to a different place that had more to offer them in the way of socialization and things to do. They were perfectly happy where they were at, but moving them was the best thing I've ever done! Now they get field trips, plenty of outdoor time, interaction with many kids their own age, plus they teach them so much! My in-home care provider also did preschool, however, it was on a much smaller scale. If it's possible for you to take the baby to the in-home care provider and leave your older daughter where she's at, that would be my advice. It might be kind of a hassle at times, but for the money and the type of care, it may be worth it. You have some tough decisions to make...good luck in whatever you choose to do!