If you are going on a cruise then the 28 would be fine on the ship. Once you get off, you will need something more substantial in my opinion. For our 4 month World Cruise I bought a Tamron 18-250 for the K100D. No regrets at all. Not the lightest combo but I always have the focal length I need. The main issue is that you usually don't get to chose how close you can get to the subject or to compose by moving around.
Now that I have a K5, I bought a Sigma 18-250 for it, the previous equipment is now in my wife's capable hands.
Yes I know those lenses have some compromises but I avoid the risk and mess of changing lenses in a hurry (you always have the wrong one mounted when on tours or walking around) and LR is more than happy to do the lens specific compensation in post.
For around town, I am experimenting with 35 and 50mm on my tele to try out the prime lens I want/need/must have. I found 24 a bit on the wide side.
Gerrit
Photos from latest cruise (K5 and K110D) and World Voyage (K100D and Optio Z10) are at
Gerrit and Pat’s Travels