I am also a Child care worker and second what lilias said about the bath stuff and choccies especially the chocolate.
Other carers never got offended if only the carers in a child's room received a gift, things like handcream, a chrissy decoration for the tree, photoframes etc are lovely and usually inexpensive, or if you can bake home made treats are great and usually really appreciated because of the effort put into them, if want to acknowledge the centre as a whole as well, you can do that in a card or thank you note. Carers don't (well shouldn't) expect anything usually and appreciate anything that show your thanks. I agree that messages in a card are much more appreciated than the gift anyway! Good luck