wow man.. that's too bad.. sorry to hear that. I have a suggestion for your son who's stealing and hanging out with the wrong crowd. Since he doesn't want to listen to you, let him do what he's doing. Let him get caught, go to juvie, but don't bail him out. He'll get caught one day and come begging back to mom and pops for bail money. Say tough luck.
As far as your 12 yr old goes, MAKE her do her chores, and help her mother. I know if I did that to my dad, he'd grab the back of my neck and whoop my ass. hed also get in my face and scream at the top of his lungs. Sometimes parents go too easy on their children (not intended to you in particular) and they let a lot of shit slide... Assign her chores to help out. If she doesn't listen, ground her. If that doesn't work, start taking away things. Be a parent. Not their best friend.
One of my biggest pet peeves when I have children will be defiance. If my children EVER defies me, shit will hit the fucking fan and I'll beat the living shit out of them.. As long as they're under your roof, they go by your rules.