How is anyone going to discover that?
You're going to have a minimum of a /64, noone is going to scan that looking for devices.
Even if they do, your firewall is not going to allow the traffic unless you've explicitly configured it to do so.
The only way someone will discover devices, is by analysing outbound traffic you make. Outbound IPv6 traffic will come from randomised addresses so the addressing information is useless. Other things disclosed by the devices (eg user-agent headers on web browsers and other fingerprintable data) are protocol agnostic.
