My suggestion:
Quote: Pentax DA 10-17 fisheye
Pentax DA*16-50mm
Pentax DA*50-135mm
Pentax DA 55-300mm
Pentax DA*300mm
Tamron 18-250mm
Sigma 50-500mm
Kenko 1.5x Teleconverter
Much as I love my DA18-250, I'd leave it behind if I had the rest of your kit. But, have you any faster glass? Some old Fast Fifty maybe? Because some cruise fun happens indoors, or ashore in the evening. Based upon my past (lousy) cruise experience, where I took 25 lenses but used about 5 of them, I'd say that ultrawide/fisheye, ultralong superzoom, and faster primes, are just the ticket. I have no DA* nor Ltd lenses; my current cruise kit (were I to subject myself to that again) might include:
DA10-17
Tamron 10-24
Zenitar 16/2.8
DA18-250
Vivitar 24/2
FA50/1.4
MacTak 50/4
Nikkor 85/2
Tak 135/2.5
Sigma 170-500
Why take a bunch of lenses cruising? Because you CAN! Why did I take MANY lenses on my previous cruise? Because I went on a multi-month drive afterwards. Why do I have so many wide lenses on my list? Because I LIKE wide; and because each is a different tool for different situations.