How exciting for you all! And that was very thoughtful of you to send the etiquette info - as a Protestant I would not know without looking up the info but would absolutely want to show the proper respect and in the rush and excitement of the trip some might not remember to check details themselves.
oh i know no one would intend to be rude, and you wouldn’t think so but the head covering applies to all faiths not just catholics. i recalled seeing laura bush with a mantilla when they went over for Pope JPIIs funeral, so i figured it was mandatory. xshub had me order his staff person a mantilla to insure she wore something.