If you were to do it at the beginning of your trip, we recommend prior to your Saturday departure if possible. If you prefer Saturday, you should get dropped off at the Pride of America by 5 pm, although to guarantee it, you would need to do a private tour.
If at the end of your trip, with a scheduled cruise ship return to Honolulu of 7 am on Saturday, that would be enough time for pick-up at the pier for this tour (8 am). Or if you're staying longer in Oahu, pickup in Waikiki would be around 7:30-45 am if you want to be picked up at your hotel after dropping off your bags. Or you could consider doing a later date.
If you are doing this tour on the same day you start or end your cruise, luggage should not be brought on tour, so you would need to store at your hotel front desk, or store it at the cruise ship terminal (Pier 2, $5/bag) beforehand and the tour can pick you up and drop you off there.
Some hotels provide a service to drop off your luggage at the cruise terminal for you. For example, the Waikiki Beach Marriott Resort and the Hilton Hawaiian Village Resort have provided such a service for the Pride of America cruise ship; please inquire with these lodgings for details and to confirm this service is still offered.