I remember having this very same delema with my first baby... I feel for you cause I know how hard this desicion is for you to make. But don't worry because your are the mother, and you know best, and you will make the right decision.
Here is my opion:
Eight months is still young, so your little one can't really interact or play with other children yet. So I would keep him/her with lady who is able to spend all her time careing just for your little one. You know you can't go wrong there. I don't know what your working situation is like, but would it be possible for you to spend weekends with your nieces and nephew. That way your little one is still able to see other children. Then once your little one is mobile and able to comunicate you can send him/her off to play school.
Sending you a (((hug)))