In order to get an in-person passport interview you need an international trip within 14 days. R(21M) needed 1 and was given a 9:30 appt, same day they pushed it back to 11, picked it up at 1, was on plane to Paris at 6pm. So it is possible. There wasn't an additional fee to have it at the State Dept (Hayes & Van Ness in San Francisco so local for us).
Research your ports to see if they are covered under WHTI (Western Hemisphere Travel Initiative). Some Caribbean countries require a passport.
https://www.cbp.gov/travel/us-citizens/western-hemisphere-travel-initiative
https://familydestinationsguide.com/do-you-need-a-passport-to-go-to-the-caribbean/