I don't get the feeling anyone who answered you has been there for various reasons, so I'll tell you what I saw:
1. It is unbelievably safe. I went wandering one night and found myself on a completely deserted area behind 2 women. Instead of being nervous like they would have if this was happening in my own hometown, they just laughed and talked. They had no fear, because it is so safe there. Islamic law is a little rough on criminals, even suspects, and it makes for a very safe society.
2. You probably won't blend in with them, even if you do physically, you won't because of your clothes. Very pleasant peolpe will figure out you're american and yell things to try to get your attention (I'm black so they'd yell about how great Muhammad Ali was) so they can sell you something. They've gotten very good at telling where people are from, they can differentiate from white americans and white germans for exmaple. The sales process is far from pushy, they offer you tea, act very friendly towards you then hope you buy something.
3. Egyptians are unbelievably kind people, they are very friendly and welcoming. The only people I've met anywhere who were as nice or nicer than them were in Brazil and Thailand.
4. As friendly as they are, they will raise the prices on everything once they figure out you're american! Be prepared to bargain, especially if you go to the Khan al Khalili (biggest bazaar).
5. You do have to be careful about drinking water (has to be bottled) or consuming any dairy products. You also have to be careful about food bought from street vendors, or fruit that may have been washed in local water (they can handle it, we can't).
I think you and your father will be very glad you took this trip and look back on it fondly for years. Cairo is one of my favorite cities in the world.