[tor-relays] Smallest, cheapest, lightest computer for tor relay

I've got a few family members across the country who have broadband they are not using for more than email and social. I wanted to go about setting up a relay at each house can can be run with minimum amount of power and attention. I was considering something like RaspPi or Compute Stick.

Main questions (1) anyone else use these or something similar? (2) recommend of strong alternatives suggested? (3) is there something smaller, lighter and cheaper that will do the job? (*) did I maybe miss something obvious that needs attention?

Thank you.