This is very untypical of JWs. Are you sure that is what they were?
JWs might ask to come in and chat but they usually won't contact a person for another couple of weeks. And it almost never is a few people who come back. Almost always it will be the same couple of people or one of them and one other person. I just can't see them asking if it is OK to bring a group.
I suspect they aren't JWs. They could be another group or what would scare me even more is people scoping you out for something.
Either way my gut says don't let them back in