Karen......you are right - Satin/SG it is easier to clean - it is also less likely to mildew - because the surface is slick - harder for mildew spores to stick.
Having said that, if this is a powder room - or a bath that isn't used a great deal - a flatter paint would be fine - you just have to be careful with how you wash it.
Behr paints are all on the shiny side - if you get their "Flat Enamel" - it is really an eggshell finish - and is washable.