You could always invite him over to check it out, just to see how he reacts to it, and if he's interested more in the tech aspect or the music aspect. Due to the increased rarity of the device, you'd probably want to find out if he would actually use the device, or try taking it apart to see how it works. I'm not sure how old your daughter is, but you could try asking her if she would be upset if you allowed the neighbor to play with the device, just to avoid any ill feelings.

It sounds like you've got some great options either way. I wish I had a neighbor growing up that had cool music gear (although I did get to grow up with a dad that got me into computers before I could read, so that definitely built my love for technology). Sounds like you're the kind of dad more kids these days need in their lives.