Mallorca is one of my favorite islands. Many famous people and celebrities have lived there. The King and Queen have a residence to use. Lots and lots of tourists also visit, so there are oodles of activities available. Please be aware there have been protests due to the heavy influx of visitors. I have stayed on the island for a bit, so I was able to get all around. I also like Menorca, the smaller neighbor.
Palma is very lovely and historic.
Hopefully your cruise ship will run shuttles from the port to the center of the town.
Once you are in the center area, you can visit the Cathedral, walk around, shop, and enjoy the water views.
Or you can head out to a beach, or take a small boat ride.
On my last visit on a cruise ship, we took a ship tour that also took us up to Castell de Bellver, but you had to pay extra to go inside.
Many people like to head to Valldemossa and Sóller for the day, very lovely smaller villages. Frédéric Chopin and George Sand spent time here. Or you could do an excursion to Drach caves, quite mysterious.
I think there is a little train you could take on your own, but there have been multiple complaints about timeliness.
Mallorca is the home of Majorica pearls, lustrous imitation pearls that have been popular since 1890!
You can check out Viator to see all the various tours and operators, and compare the price to your cruise excursions.
I would love to return for a week or so once I retire from working, but I will try to avoid high season.
Have a great time! ¡Buen viaje!