I was going to suggest checking out Iberia, but you don't have AAdvantage points. Which airline does the 60k UA itinerary?

Transavia is becoming partners with DL soon. Not sure if the dl engine will find you awards on Transavia yet. I'd gladly burn 60k DL before 60k UA, but you'll have to find out if there's such an award to choose between burning DL or burning UA.

If you want to visit more than just Palma, you could also fly to a larger European city, and get over to Palma on Easyjet or RyanAir.