Coupla ideas to add to this wonderful mix.
Don't use balsa wood, too costly, use spaghetti instead. Easy to get, cheap, breakable, comes in different thicknesses.
For the senses prepare containers with different things in them, eg a leaf, pinecone, something furry, some cold cooked spaghetti, smooth stones etc. Have them in opaque sacks. Blindfold individual students and they can feel what is in each back. The blindfold increases the tension, so when they feel something strange eg furry, or cold and wet they can be quite excited.