Be careful if he's reluctant to move back in.. that means he's still all doped up on his affair.
Separation does NOT help reconcilliation.
Was he having an affair when you asked him to move back in before?
I would tell him it would be helpful for him to move back in but he would be staying in the guest room, that you need help maintaining the home and raising your kids. That his involvement is important as a father. That the two of you sharing a bedroom is not part of the offer.
And don't push it.... leave it there just as is...
If he declines... its a good indicator the affair is still going on and he wants easy access to come and go as he pleases.
I am just trying to figure out how to express distrust without antagonizing him... let me work on that.. Pupper may have some ideas on that...
He needs t know he WON'T be trusted as long as he's living elsewhere... He NEEDS to know that without it being phrased in a way that will antagonize him and do damage.