You don't offer to drive her. Nicely have him deal with his decisions. Take some kind of a class Friday nights that keeps you from being tempted to do it. I take a yoga class every Friday night that my H has the kids so I'm not tempted to take him up on his often offer of dinner as a family. It ends up with the whole family dynamic, which in many ways I like, but me doing half the work. We eat together often during the week and I'm fine with that, but like to make him stew in his situation. He says the house is empty without me, that it's harder to be with the kids and without me than he thought it would be. Make your H realize some of his realities in the situation.
Me: 42/H: 37 T: 10 years/M: 8 D9, S8 Bomb: 7.23.07 Separated: 1.20.08 D Final 3.19.09 Affair started in '05, found out parts in 11/07. They married 11.26.09