The fees are very reasonable, for 40 LE you get to have a "tour of the Nile" (a walk through a fake safari along the length of a model Nile, a visit to the museum (one floor only per visit -- don't bother asking why), an activity for your kid (painting Nefertiti on papyrus), and an enjoyable stay in the gardens which have one of the best and safest children's playgrounds I've seen in Cairo and even feature a butterfly museum (seasonal).
It is clean, highly under crowded (one of the few places - truly undiscovered so far by the masses), and I'd rate the interactivity and exhibits of the museum itself as better than the ROM in Toronto.
The first floor has Ancient Egypt and this is just awesome. It includes large rubber Sphinxes that kids can assemble like a puzzle, wall drawings, an X-ray scanner of a mummy and a replica of King Tut's tomb. Next floor up is agriculture, then the desert and the sea, and the top astronomy (top two floors are reserved for schools but with a bit of convincing we got to see the desert/sea floor minus use of some of the electrical gadgets).
Awesome, not to be missed by any family coming to Cairo.