I would choose one of the older ships. Sapphire would be my choice. More venues, better viewing areas. While the Majestic is a nice ship it has the potential for 1,000 more passengers than the Sapphire with not very much additional public space. The Majestic was built for the Asian market and is somewhat different in design and venues than other Princess ships. All three ships have an indoor pool.
The Alaska itinerary attracts families. There will be youth on board when sailing during school summer school vacation period, June through August. No rock walls, bumper cars, surfing, ice rinks or anything like that on any Princess ship.