They are trying to find a warm place. Plain and simple. If you will check around, you will see Lady Bugs doing the same thing.
What we used to do was slip up to our big enclosed blind, ease the door open and put a can of insect fogger inside, set it off and close the door. Go back an hour or so later and the problem would be pretty well taken care of.
Then we would keep a can of wasp spray in the blind and any time we saw a wasp, it got sprayed.
Until it freezes, I do not know of anything that will repel the things. They are going to try and find cracks and stuff to crawl into, and they will pile in them by the hundreds.
Probably what the Dr. gave your Dad is an Epi-Pen. it contains Epinephrine, a steriod, that helps open the bronchial tubes so that the person can breath. Most allergies immediately affect the lungs and the trachea.
Lora has the same condition and she carries one with her everywhere.
Odd thing is, that where she is allergic to wasps and bees, I know of at least two times in the past two years that she has been stung by a scorpion and had no ill effects, other than the area around the sting hurting for a couple of days.
The thing you have to be careful with, is that your boys have not inherited that same allergy.
Until or unless it freezes the wasps will just continue to be a problem. JMO.
Maybe someone else knows of some form of repellent.
Good Luck and Good Luck to the boys this weekend.