What to do about my sons friend..Help Please!!

Tweet

My oldest son is 9 years old. His friends are a major part of his life. He really is a sucker when it comes to his friends and will do just about anything for them. I think this stems from his speech problem that he had as a young child. At age 4 he still couldnt speak and it was very hard on his self esteem when another child would ask him his name and he couldnt answer ect. Now at age 9 his speech is fine and he has lots of friends, but it seems as though he is very frightened to upset them in any way. I think he is afraid to say NO because he doesnt want to lose them as a friend. Anyways, his best friend( friend A) who is a good kid, is away in Mexico. So Naturally my son will turn to another friend ( Friend B) to hang out with while friend A is away. My son doesnt normally play with friend B because Friend A wont have anything to do with him, because he beat up his twin sister. So as you can see friend B really isnt a nice kid. Friend B isnt welcome at friend A's home, which is across the street from ours. Friend B gives as bad vibes. We have seen him trying to open our garage, for what reason we have no idea. We have seen him in parts of the house that we are not sure why he was there, its just seems that whenever friend B is around something happens, and my son usually ends up in trouble for something or other and its usually something that would not normally happen. If I tell my son that he cant play with friend B he will be very upset. probably to the point of tears cause his friends mean that much. So what should I do? I dont want friend B around my son at all, and I know that he will be out of the picture as soon as friend A comes back in 2 weeks. Do I wait it out or do I put my foot down and say NO even though I know it will break my sons heart?