Aswan
Aswan High Dam and Temple of Philae (Aswan) - Two big attractions at Aswan are the Aswan High Dam and the temple of Philae. I didn't think the dam looked like much, but my kids loved the diagrams showing how the dam is constructed and the huge expanse of Lake Nassar behind the dam. And in fact, damming the longest river in the world is a big deal.
The
temple of Philae is fun, in part because it is on an island and you can only get there by boat.
Editor's note: We saw the Aswan Dam and the Temple of Philae as a day trip from Luxor, but it's really too much for a day trip. You're better off staying off in Aswan as your starting point.