I am running Unifi's controller to handle 2 APs and 2 switches at my house, plus 3 APs, 3 switches, and a USG that are remote (at my parents' house). I currently run the controller on a Synology ...
Alternatively, set them up with their own Cloudkey and enable remote cloud-access (via https://unifi.ui.com) to be able to manage their network, and pray and hope the mongodb on it doesn't shit itself ...