It's the thought that counts. A handmade card your daughter helps you create thanking them would be enough. Homemade cookies you wrap up, with a thank you card, too.
I'm on a fixed low-income and had three to gift yesterday, 2 teachers, one aide, and spent about $30 total, I purchased things here and there to spread the cost out ;) I made up cute orange sand pails with all orange goodies inside and on the front of the card's pictured orange I wrote "Orange you glad it's summer?" Inside I wrote my heartfelt thanks for helping my guy throughout the past nine months. The teacher's aide was so shocked and touched, she burst into tears. (She is such a dear woman, like another Gramma to my guy, there's no way I would have left her out.)
My point, don't feel obligated to gift certain gifts. The main thing is you express your "thanks" and appreciation, don't worry about being "cheap."