Since surge protectors are a fire hazard on cruise ships, and the person that's going to be trying to determine if it's a hazard isn't one of the ship's engineers, I can easily imagine them erroring on the side of caution and taking it from you.

However, if your concern is being able to charge your phone, tablet, & notebook in Barcelona, then chargers for these devices work just fine on 220v, you just need a simple adapter to plug it in.

Like this

Your sister's gift is pretty cool, I'd hate to lose it.

Enjoy your cruise!