Royal CAribbean is a great line for all ages. Alaska is a very active destination so I think young adults would like as long as they want to do active excursions on land.
Luisa Frey Gaynor
Family Cruise Editor
Hmm....not sure on that one. You certainly won't have grade school kids on board until June when school is out. I have a feeling you would have more young adults on board during the June-August period when the rest of their family -- who may have young kids -- might be sailing. Plus, in May it will be chillier for doing the many outdoor active excursions that young adults might like such as kayaking, dog sledding, hiking, etc.
We took an Alaskan Cruise last summer and two in our party were 18 and 19. I would say that if you gave an 18 year old their first choice, they would choose Mexico or the Carribean. Which, we have done, and they loved it! However, with that said, I would NOT say that they would be bored on an Alaskan Cruise. Our kids REALLY enjoyed the helicoptor tour and dogsledding tour. That was a highlight for all ages in our group , 11-65. Also, the older kids did enjoy hanging out with their younger siblings and I'm sure made lots of funny memories. The olders usually don't take the time for them at home, so it presents a situation that is not the norm. The majesty and beauty is a little bit lost on this age group, but in my opinion, they are lucky to have the experience. When they are paying they can choose the destination!