0k I am gonna play th cynic here. This looks like someone who. Wants to try pit his options and keep the saftey net o his marriage. Its the old 'we were on a break.' excuse in the prepping.

8t may be that he doesn't know what he wants, but why are you expected to wait at home twiddling your thumbs waiting for him.
You
Best be sure he knows cheating is still cheating when you are separated. If you are going to go along with this I would be setting out some very strict ground rules,. Especially surrounding the kids, he doesn't just get to walk out on them. Make arrangements for the evenings and weekends he is to have them. He wants to tial a separation then make sure the arrangements are those you would expect if you were separated.
Dont let him treat this like a holiday from the relationship whilst you are desperately trying to figure out how to fix things.
Dont simply allow him to call the shots on this, its your relationship too.
If he has any sense he will attempt marriage counselling first instead of running away.

Really do wish you all the best.