Arcadia is easily the best in Cairo from what I was told and experienced - next to Conrad Hilton.

If you want good clothes that are well made, especially kids stuff- definitely check the mall out (3rd floor for kids). Khan el Khalili will not give you certain things and quality can be patchy. Mobaco (very common in big hotels as well as Arcadia) chinos and shirts are as good as any thing from good western brands and cost 60% less - 95% of the time they wash really well as well.