I saw some pins on pinterest that showed a cord with keys on them. The idea was that the kids could play with them and they would make a neat ‘jingle’ sound.
I asked a home depot employee for some miscut keys, and the manager was glad to oblige. It worked… for a while.
Eventually the rope I put them on was cut from the friction and then keys ended up everywhere.
I’ll try again someday, but I’ll have to put them on a wire or rope with wire inside or something. Another option might be to string them separately like a wind chime.