L.C.
I put my girls in a daycare center, for some of the same reasons you stated. If someone gets sick, they can still be cared for. Also, I just felt better knowing that there were many people around, to hopefully prevent any inappropriate behavior ( by the caregivers).
I have not regretted my decision. Once the kids get older they need the interaction with other children.
Since your daughter is only 7 months,and she may need that one on one more now, you could leave her with the nanny, until you feel she is ready for some more interaction with other children.