This is my instruction/explanation for communion at Catholic weddings or funerals (I welcome your observations, but I hope they are respectful):
"This is the time during a Catholic Mass when we make our communion with the Lord and receive the Body and Blood of Christ...

"...You can process up the center aisle in two rows and return to your seat by the side aisles.
If you are not Catholic, or you haven't made your First Communion, or you are not prepared to receive communion today..."

...but you still would like to participate in the procession, you may come forward; when you get to the minister, you can place your hands across your chest like this [I demonstrate]...

"that will be a sign to the minister that you would like to receive a blessing instead of receiving communion [btw I say, "May the Lord be with you" for the 'blessing']. If you prefer not to participate in the procession, you may remain at your seats for sung or silent prayer."