Elf house on a tree! That would be cute in the garden, especially in the tree over grown with ivy. How about some battery tea lights in the windows during outdoor parties. I hear the fairies/elves whispering "home school project" in my ear.
Craft with the kids this summer DIY garden stones - use a cake pan! Also, using clear contact paper to hold the mosiac pieces in place while the concrete sets is also kind of brilliant. I want to use mirror pieces, red gems, and black cement dye.