My son is 10. He has two close friends - let's call them Bill and Bob. My son asked if Bill can come round after school tomorrow, I have said yes.
Today at school Bob said he will come too.
In April I took Bob on a day out with my son, and his behaviour was dreadful. Really, really awful. I swore I'd never have him over or out again. I relented I'm June for my son's birthday party and Bob was a fucking nightmare, I'don't never seen the likes before (or since). It cemented for me that he won't ever be welcome back in our home.
Now, he has invited himself to the playmate tomorrow... I have three options that I can see. A) if he does try to come tomorrow, explain he can't come because of his previous behaviour. B) send his mum a message in anticipation, just saying it's not suitable for him to come tomorrow (I don't know what the boy has told him mum about tomorrow afternoon), C) let him come to avoid my son having to face a potentially awkward situation at school.
Not to drip feed - my son does not particularly want him here and thinks he was rude to invite himself.