Hey Stephen,
Since the IP is static can’t you just tell the new owner “Hey, to use the Sprinkler open a web browser/app and type in the IP ‘10.0.0.50::8080/#sprinklers’ address and this is the login:password. Also that IP address is Static which means that when you set up your new network it has to be ……’
Obviously they will want to set up a new SSID/password but it may ease the process. Paint by numbers is right but TBH they are getting a great system.