H.:
I like to get "teachers" of all sorts (ballet teachers, mothers day out ladies, sunday school) something they can really use, or use up rather than something that will sit around and collect dust, considering how many gifts they probably get in their careers. Also I think of something that the kids can help pick out and can be consdiered from the kid rather than just from you. Things like: cute fun socks from target (letting kids pick them out), nice travel size beauty products like aveda, candles. Or have the kids make them things like ornaments or bracelets that you can get kits for from a craft store; Of course baked goods are always a hit, and can be fun for everyone to make together. I also have given a card with the kids' picture on it, sometimes in a frame so that the frame is reusable and they get the picture for as long as they want it. For people who own facilities I might get something they can use there, like kids books for preschool teachers.
I have thought about the books for adults thing before, but they are so hard to pick out and can tend to send the wrong message, and since people who work with kids don't have alot of on the job time for reading up on work, they would have to read about it in their spare time and who wants to do that? Gift cards to a bookstore/coffee shop are always good, but can really add up considering that you don't want to put $5 on a gift card :)
I do know that they appreciate your thoughtfulness in giving them gifts, and it is a wonderful way to sincrely express you appreciation of the loving care they give your family. A good lesson to teach your kids too, about why and how and who we give gifts to.
Good luck ...
A.