how explicit, what is actually expected by each party. Clearly 'cheating' is not a legal term here, so it really depends on your 'understanding,' but certain acts might violate the laws of your State.

then, no worries.

it's best to take the high ground and not do anything that would otherwise be considered "cheating" until you've at least separated.

Also, if you're staying together because of the kids, how would they react to your "cheating"? How old are they? Have you told them anything yet? The answers to those questions matter.

Meanwhile, my personal advice, knowing nothing at all of the details of your situation, is to seek legal advice, and move in the direction of legal separation or divorce as expeditiously as is reasonable.