You haven't mentioned some of the points that dictates what anyone offering advice should know - what is most important to you? Is it critically sharp pictures or carrying just one lens? Another factor, which someone else has mentioned is - will you want large blowups of any of those pictures. And I guess one other is are you going to be carrying a flash unit or relying on the small, built in flash on the camera.
Now, to answer those questions. If you want critically sharp pictures because this is a "once in a lifetime" trip, then I would carry two zoom lens. This would allow you to limit the zoom range and you would lose less sharpness. The extreme zoom will lose quality - period. If two lens is your decision, restate it and you will get a lot of different answers.
The point above, using two lens, will also allow you to use faster lens, therefore allowing you to take better pictures when you have less light and a small flash unit (built-in).
Another question I would have is do you have good post processing software programs such as PhotoShop and LightRoom? If you are going to be printing pictures right out of the camera, you are going to want the best photo you can get. Those programs can correct many an exposure mistake but not all. And, you would have a huge learning curve.
If you go with one lens, try to not use either extreme ends of the zoom range, which will be where you get the poorest quality, most distortion, and smaller f stops.