I wouldn't force it.
I'm curious about just why his friends are bad influences, and why you don't approve of ANY of them.
Here's the thing about "bad influences:"
We teach our kids good values and morals beginning at a young age. We show them the difference between good people and not so good people. And then we let them make choices in actions and friends.
If this kid isn't a "good influence," that doesn't mean that you should immediately pull your son away. You should gently ensure that your son is aware of the inappropriate things this kid is involved in, and ensure that your son understands that it's not okay. You should have this kid over to hopefully have a good influence upon HIM, and keep (quiet) tabs on what sort of relationship he has with your son.
At 12, it's time for your son to start learning to choose rightly for himself, with some gentle guidance.
Ask him what sort of activities he'd like to be involved in. Why can't he be on a sports team with his friends? Why not involve him where he's interested?
ETA: I'd call the scout leader and find out if there is some way that they can help make the camping trip happen for your son. I think it'd be good for him and he'd really love you for trying.
"Reason we can't send him this weekend- husband can't get off work to go with him and I can't because I have to watch the siblings. Husband doesn't want to send him off an hour away with strangers."
He's a boyscout! He goes to school 8 hours every day with strangers. He NEEDS to be able to participate without mommy and daddy. Contact some of the other parents for the list. I'm sorry for sounding mean, but I think your reason for not sending him is lame.