Marcimommy- I didn't see...how often will your LO be in her care? I know that my dd is only in a sitter's care for two days per week, and it really doesn't upset the routine if for some reason she is unable to keep to the "perfect" schedule. I just get her back on track when she's with me.
I think it's important to decide on a PRIORITY. I told my sitter, if her naps are off because of extra activity or whatever at the sitter's place, JUST KEEP TO THE FEED SCHEDULE. I found that focusing on one detail as the most important left enough room for error, and still kept a rhythm to her day. The feed is at 11 and 3, no matter what....and now solids at 12:30. It has worked well for dd, even though some days she comes home overtired because of activity around her during naptime, she bounces right back on days she's at home with me.
As important and valuable as a routine is, I found the most important thing for my own peace is that she LOVES her sitter and is HAPPY when she comes home at the end of the day. No matter what else happens (and believe me, I LOVE MY BW!!) as long as my daughter receives TLC and is somewhat held to a flexible schedule, I'm happy. And she's happy.
Don't stress over what hasn't happened yet, either. Our babes are SO ADAPTABLE. Follow your heart and let your lo let you know whether it works for her.
Best of luck, and in the long run, you'll know what's right for her....but sometimes you just have to jump in with both feet and hope for the best! My thoughts are with you.
-Anita