Does the vocal range of people 65 and over change (i.e., do they lose their high notes or low notes)?

I have volunteered to lead a group of seniors in a Christmas carol singalong. I want to arrange the songs in keys that will be suitable for their voices. They are average women with no real singing experience. I don't want the vocal range of the songs to be too high or too low for them, so that they can really sing along and enjoy the experience.

if its just average yes just like anyone that doesnt "work out" their vocal chords then you will lose the extreams of your range.