For the Acquaintance
Do not feel obligated to give a note or gift to all the mothers you see throughout the day.
Your mail lady and the cashier that rings up your groceries every week are not expecting a surprise from you.
For these mothers, you can say “Happy Mother’s Day” if you see them, but you don’t need to go out of your way to contact them.
When you see them afterwards, you can simply say “Hope your Mother’s Day was nice!”