3 days or 3 nights? Two different things. Be careful as to what counts for a "day". Also, add another day 'cause you're gonna wanna be at the port the evening before. So don't forget to account for that transfer, hotel night and meals. I really, really wouldn't plan to fly day of (no matter what some might tell you).
All that said, for a 2-hour flight (especially with the way travel is now), I don't think it's worth it. You'll unpack one day and pack up the next. 2 hour drive, sure thing. If you've never been on
DCL, yeah, it's an inexpensive way to learn about their cruising. Me - I consider anything less than 8/9 nights not worth the effort at this point so take what I say with a grain of salt.