My 'opinion' is: Drink package is worth it. You can get special coffees, bottled water, and alcoholic drinks. Carnival has one of the LEAST expensive drink packages out there.
Excursions - first cruise - Again, I would use Carnival's excursions. They, again, are some of the CHEAPEST excursion prices out there. NCL for both above mentioned items are insanely expensive.
Cruise excursions - You will ALWAYS make it back to the ship.
Private Excursions - You 'MAY NOT' make it back to the ship in time for departure. FYI ... Traffic delays. Cars break down/flat ties, etc. There's no AAA out of the country.