I hope the mother isn't a LI. If she is, this question is a terrible idea.Even if it isn't technically NTR. In any case, it would be nice to also be able to deactivate the voyeur scenes (and if they don't happen that way, even better)
Anyway, I have no intention of watching what happens in that scene.
To be clear, whether it's NTR or not, any sex scene where the MC doesn't participate is a scene I don't like and would prefer to be able to avoid completely if the girl is a LI.