cheating avoidable¿? is cheating on the mc or the mc cheating?¿
Cheating will be avoidable (just like in real life) that if you don't want someone to sleep (i.e.: not have sex) with someone else, you can choose to keep them from having sex with others...
...however, on a side note, being that this is an EROTIC game, it kind of doesn't make much sense to play an adult game and not get the person laid.
My suggestion is play the game, if you don't like the game or if there is content in it that makes you upset or feel queasy then don't play it... simple as that.
As the writer, I don't know what your tolerance is... only YOU can determine if it is in your 'comfort level' or not.
Personally, I don't understand why guys think it is okay to fuck around on those that they are supposed to love or are married to, but it's NOT okay for their girlfriend/wife to do the same...
In my opinion: What's good for the Gander should also be good for the Goose as well... and vice-versa.