M.L.
In the past, I asked my caregiver's husband about personal gifts, specifially a massage gift cert. He said she has never used them because she doesn't have time. I gave her a mani/pedi certificate that included mani/pedis for her two oldest girls also. They had a mommy/girls day at the nail salon and really enjoyed it.
This year (different caregiver), I am going to give her a gc to a very nice restaurant for date night with her husband. They are recently married, with an 8 month old, and her M. will watch the baby for them.
I agree with the other posters that you give what you can afford, and what you think she will like. I also keep in mind that this woman cares for and loves on my child every day, and I want her to know she is important to us.