I wouldn't be happy if someone grabbed my son either.
But yours has hopefully learned a few lessons from this.
Mainly not to piss people off by harassing them in their homes.
And if he really was just standing by and watching his friends do it, then maybe he's also learned to pick better friends.
Not only because they are happy to bang on doors and run away, potentially frightening whoever is inside, but also because they are happy to run away and leave him to take the blame.
And also not to lie about where he lives. At least he was brought home to the right house, not to a house full of strangers. And if he was in tears, as you say, you'd want him to come home.
She said her children were scared. Whether you believe her or not, you're unhappy that your child was upset, so you should at least try to see where she's coming from in not wanting her children frightened by a group of high school boys banging on the door every day.
Because if they get away with it once, they'll do it again and again.
You say she wasn't old, but did the boys know that? Do they know if there are young children in the house? Do they know if someone in the house is ill? Do they know if someone is disabled and struggles to get to the door? Do they know if the occupants have recently been burgled and so feel vulnerable? Do they know if they've been victims of violent crime? Do they know if they work late shifts? Or have a relative in hospital, or care for someone, and so are exhausted and just can't deal with crap like this literally at their door?
Do they know anything at all about the people they bothered that day? Do you?
You've posted about your husband. Ask your son how he would feel if a gang of lads messing about banged on your door and ran off if it bothered his Dad or stopped a member of your family for caring for him while they went to answer the door.
So again, no I would not be happy about someone grabbing my child, but if he's not hurt, I think you need to accept that he was the one really in the wrong. And if you do have a word then you maybe need to be apologetic than accusatory while you discuss it with them. And don't use the word "assault" when you do it.