Depends - is there money for a motel room? If he can afford to rent a room, he should. On the other hand, if that's not economically feasible, him staying there is probably what's best for your kids. Also, it's an opportunity to let him think about what he's leaving behind. Can you arrange to go out to "meet friends" on those evenings (all dressed up nice, with perfume on)? Come home late - I don't care if you're just sitting reading at the local coffee shop. Assuming that he, like most WASs, is having an affair or left in order to pursue dating, most WASs don't even think about the possibility that YOU might be pursued by members of the opposite sex. They think you'll just be sitting there waiting for them.

Note - I am NOT suggesting you date. Just be busy and a little mysterious - let him fill in the blanks. And take full advantage of the "free" babysitting.