Not sure what those round grey parts are. They have a blue "light" on them. My son has almost exclusively Star Wars sets but we can’t figure out what these are from.
Welcome to Bricks.SE, Laura! These pieces are not very rare, and hence finding the set they come from is going to be pretty hard. With your hint that your son only has Star Wars sets, I think this is from 75166 First Order Transport Speeder Battle Pack, where these parts form the engine outlets of the small vehicle.