Ding dong ditch the house (when the girl is home) leaving a big bag of flour that has clearly been opened and then retaped shut. She’ll go nuts searching through the bag of flour for a message. Then have your son wait for awhile and return with a flower, ring the doorbell and sheepishly say something like “I left the wrong flower”, then give her the flower and accept the invitation face to face.

This worked like a charm back in the day. My date spent an hour with her mom and best friend sifting through the flour trying to find a clue of some kind. There was flour everywhere - all over her hair, clothes, etc. when I came back with a single rose, she just melted. And then we were able to talk to each other in person like humans used to do.