The cruise boats are quite notorious for passengers getting delhi-belly. As long as you know.
Or you could stay at Luxor and take excursions - we used the St Joseph hotel which is simple, clean and incredibly good value. you can watch the cruise boats from the rooftop bar (with pool), watch the balloons coming over at dawn or even take a ride in one, walk up the corniche, get the living daylights mithered out of you by caleche drivers ---oh, and shop at Arkwrights....honestly......