I see the answer to this question as a way to preserve the legal marriage with some remote form of "intact" status at all costs—even though the situation created by it defies what we usually think of when we think of "being married"... The question is, does this not give children too much power, basically proving to them that they can successfully cause a separation?

...I don't know if kids really care so much whether or not their parent is still "seeing" their spouse elsewhere; but they'll know that they have essentially won a battle not meant to be won (i.e., let no man put asunder) and that whatever they did to get the new spouse out of their (parent's) house worked/works/can work again...not to mention the fact that their friends observe the same...

Seeking alternative points of view...

I'll be frank, I don't understand the question. You seem to ascribe a lot of power to the kids, I don't see how kids have more power than their parents allow them to have.