The teen clubs can come and go as they like, its just Oceaneer Club and Oceaneer Lab that need booking
Currently on The Disney Magic UK
To help manage capacity, parents must register their children for Disney’s Oceaneer Club and Disney’s Oceaneer Lab during the Online Check-In process and then, prior to setting sail, reserve specific session times online or via the
Disney Cruise Navigator app. Guests can book one session per day on a first-come, first-served basis: a 1.5 hour-long session on Embarkation Day; and a 2.5 hour-long session during days at sea. Children will receive their youth activities wristband at the cruise terminal, which grants them access to both Disney’s Oceaneer Lab and Disney’s Oceaneer Club.
Pending availability, Guests can also register their children and book session times on board the ship using the
Disney Cruise Line Navigator app.