Grab the Sonos FAQ section and do a Factory Reset of all the devices you are giving away then take them to his place and follow the New System setup steps to get it back together.
Factory reset: https://support.sonos.com/s/article/1096?language=en_US
Factory resetting is typically done when you are transferring ownership of the player or want to register the player to a different email address. Rebooting the player is done if you've replaced your router or move a player from one location in your home to another.
New setup, Boost or Standard: https://support.sonos.com/s/article/3235?language=en_US
Standard: https://support.sonos.com/s/article/2627?language=en_US
Boost: https://support.sonos.com/s/article/3240?language=en_US