I like all the suggestions given. I would recommend using coke bottles for flute simulation. I used to demonstrate with a set of bottles in front of the class with various levels of water in each bottle tuned to a specific pitch(playing simple tunes on them like a big pan flute).
For brass I would use a piece of garden hose. In longer lengths you get the alp horn effect. A mouthpiece is not needed but a trombone mouthpiece works well. My kids always went home and experimented.
I would recommend song flutes over recorders. The Conn song flute is my favorite (not overblowing as easily as the recorders do.