From a "Teacher's Perspective"
Ok I'm not a teacher (therapist) but here's my take on things if you're interested:
I appreciate anything anyone gives me...a handwritten card is sometimes the most touching thing a parent can do. You don't have to "buy" something.
I have a little collection on my desk....accumulated over 14 years...of "stuff" given to me by students and parents. A jade carved owl, a handmade piece of jewelry, a pretty rock collection, a "made in shop class" coyote pencil holder, etc...just to give you an idea. The point is, I remember EVERY SINGLE STUDENT who gave something to me...ANYthing. A little momento, regardless of it's price or where it came from, indicates you were an important person in the lives of these kids and parents, and THAT'S all I need