To review the options go to www.carnival.com - click on the link Explore at the top of the website- click on Shore Excursions - type in your destination to review the excursions for Nassau, Bahamas.
The guidelines for booking a group excursion are below:
Need at least 12 guests to book a group excursion
Need at least 25 guest to book a private group shore excursion
Need at least 35 guests to book a custom group shore excursion