I know you didn't want comments on anything other than the car trade in, but I can't help myself.

As long as you are there to bail them out, they will never learn to be responsible with their credit. How long are you willing to cover them? They need to realize its THEIR responsibility. If they have to pawn the TV, sell the couch, whatever... so be it. Thats the only way they will learn. They need to make the sacrifice, not you. Once in a while people need help, but this is sounding like a recurring problem.