Hire a bike and tour the towns and countryside at the other side of the Nile (the Necropolis etc.)
It's definitely off the beaten track and a lot of fun. Even the Valley of the Kings is an easy ride by bike, although you have to climb for +/- 8 km.
As a rule of thumb: relax. Don't go to a temple/museum et cetra when there's an enormous crowd. Two or three hours later you may be the only visitor....
The tombs of the nobles are definitely worth it as there are less visitors and beautiful. The idea of the bike is excellent, i've done it, hard but rewarding.