Don't worry where other family members wish to cruise, it's you husband's 60th birthday, his opinion should count most. If he wants to cruise to Alaska, that's where everyone should go.
Alaska is beautiful in May. Every Alaskan port has many different kinds of activities to choose from that should satisfy everyone, except a sunny beach.
NCL will have three ships sailing to Alaska next May, although only the Pearl will be sailing to Glacier Bay National Park. It's fares will be higher than the others.
There's so much to do at every port, everyone will be exhausted upon returning to the ship. So, plan a few easy excursions during the week.