I've done this cruise many times.
For Cabo I recommend any Carnival excursion, makes tendering easier and less stressful.
For Mazatlan I've used this vendor: Mazatlan Tours, Activities, and Excursions
The Stone Island beach break gives you a brief catamaran tour, beach time, open bar, lunch and two activities each, such as snorkeling, banana boat rides, horseback riding, etc.
I've used them in PV as well: Puerto Vallarta Tours, Activities, and Excursions
There I did the city and tequila tour. Lately I've been going to Playa del Muerto, and hitting the beach club at La Palapa. It's got a minimum spend, which is easy to reach with lunch. The parasailing guys set up right there, so grabbing a quick ride is easy.
Just know the first and the last sea days can be breezy and cool, so bring a jacket.
As for the ship, I sailed on her for the first-time last year and was pleasantly surprised. Never seems too crowded. The lay out is nice. We spent a lot of time outside of Ocean plaza at the tables and daybeds catching sun and relaxing.