You know, as a preschool teacher, one of the sweetest things a child ever gave me was a homemade ornament. It was a little letter block with a jingle bell, a miniature tree and a bow hot-glued together with a loop of ribbon to hang it. I received this nearly 18 years ago, so yes, it's memorable.
You could also have your children make cookies to put in the basket, with some good tea or hot cocoa packets. Warm drinks are a treat, esp. if it's a Ghiradelli chocolate type 'fancy' treat. Holiday craft markets often offer beeswax candles, which look and smell delicious. Or make a little kit with a forcing bulb, glass container and pretty pebbles-- your local nursery likely may have some forcing paperwhites still for sale. I'm sure that whatever your family does, the teacher will appreciate just being remembered. I don't expect gifts from my families, but when one comes along, it's very special and I do feel appreciated myself!