Whereabouts are you going? Remember that some sites wo the let you bring a camera in (Valley of the Kings and Giza).
I did a Nile cruise a few years back and took my then a580, 16-80, 35/1.8 and 70-300. Most used lens from my existing data was the 16-80 at both ends, so I'd go with the 24-105 (I didn't particularly feeling like I was missing a uwa).
It'll cover you for architectural shots, internal shots and environmental portraits (you'll definitely see some interesting characters!). No real need for a fast prime. You might want something longer if you're on a boat, but 105mm isn't a bad compromise.
If I was doing it again, I'd either take my 35/2.8 and travel ultra light or rent a 24-105. Hope this helps!