I would only do ftnoob's suggestion of taking a morning flight if I took the first flight TPA-FLL, the 0710 departure. It gets you in to FLL at 0800, so you'll have time to kill there, but it's better than being up in Tampa waiting for a delayed 0945 departure that will put you to your cruise after it departs.

What I'd do is call reservations, ask to have them add a leg on your tickets. I'm not 100% sure if they can (I don't see why it wouldn't be possible) and book the evening departure to FLL on the 14th. If that doesn't work, you could always try flying in to West Palm Beach. Flight 272 flies PDX-DEN-TPA-PBI. The drive down from West Palm isn't that bad--I've done it a couple times to the Miami area. It's about an hour without traffic, straight down the 95. Much nicer than the 4-5 hour hike from TPA.

By the way, if you book PDX-PBI, you'll probably need to call reservations to force a booking on that flight. For some reason it doesn't show up in the reservations.

Good luck.