I agree with you son invite who he wants.It's his birthday and he is going to be 10.
3 little boys have made the rest of the classes school life feel so bad then I think a lesson in how to treat people kindly and with respect is well over due.
Don't do what my poor Mother did,years ago I had my first ever birthday party,I was about the same age as your son and she invited her best friends daughter,which was lovely,she is 2 years younger than me but was a lovely little girl and were still friends 30 years later.But she also invited one of her friends older sons(his own sister didn't want him there)he was bloody horrendous!Had me in tears,upset other kids and his little sister.He physically assaulted me at my own party in my own home,bullied me,he was really vile!!
My Mum cried when he left and my Dad went nuclear at my Mum for inviting him.My Mum and her Best Friend were never as close again afterwards.
I've seen lots of threads on here with the same problem,I'd say 90% said invite them all or none.Most of the OP's did and oh did they regret it.There was parents coming back on talking about the party was ruined,the child/children had hurt the birthday boy/girl/they're friends or both,had broke presents,broke stuff at the place the party was being held,stole some of the presents ect!
As adults we'd never invite someone to a celebration that was horrible to us either physically or emotionally!So I have never understood why so many expect a child to do exactly that.A child's rights are just as important as any adults!