I'm going to let my son exclude four people from his birthday party
Why would you let him exclude people?
I think his decision to exclude them is a good decision.
If you let your son single out certain people and exclude them from his party, you are teaching him that singling people out. You should ask him why he doesn't want them to come, and try to help him work out his problems with them instead of just excluding them.
He said he doesn't like them and he has good reasons.
Can you tell me what those reasons were? I'm sorry to have jumped into a conclusion. If the kids are bullies or mean then I can understand why they would be excluded.