I was worried by all the stories of ill health you hear about Egypt but no-one in our group of 9 was ill, most of us followed usual advice (don't drink the water, no salad or fruit unless peeled, use hand gel) and I think it helped that our guide had the local knowledge to take us to the right sort of restaurants.
The armed tourist police and armed hotel security men in Cairo seem alarming at first but you soon get used to it. Cairo and Giza are not places you should walk round without a guide, especially women.
The overnight train is an experience - beds OK, but dodgy loos, club car from the 1960's full of smoke but with no alcohol, and evening meal pretty inedible so take your own food (though breakfast OK). But train was on time both journeys, which is a nice change from my local trains.
Late March seemed the perfect time to go, weather wise. And follow your guide's advice for getting rid of salesmen!