It is not the kids fault of what type of family they were born into. People look very unkindly towards wife sharing, as many people have heard horror stories at how the man treats those women. Some of them are kids, and they have sexual relationships with under age girls. Not to mention they are married to underage kids. People might not have such a problem if all the women were adults and the women married the man on a consensual basis. Kids have to deal with the ramifications of their parents choices, which isn't right.
Wife-sharing should definitely be a negative influence because other people in future relationships may not see eye to eye, which may lead to infidelity, or even trouble maintaining a relationship. Because it is not the norm, people should not encourage it. The children should not be around this as it is not legal in most of the US.
Openly participating it an open relationship of any sort in front of children sets a new low moral standard for the family unit. Already the entire concept of open relationships between people are not fully functional and participate in the increasing moral decay of society, and once this is exposed to children, the entire paradigm of society will radically change for the worse.
Wife sharing causes mistrust within the marriage. Most couples, married or not, will have certain inalienable instincts about someone else claiming their mate. This will eventually lead to mistrust. That mistrust leads to an unstable relationship that is visible to the children. Children can't quite comprehend why their parents are fighting because they don't understand normal relationships yet, much less a wife-swap.
I think that couples and parents who engage in such as acts such as wife-sharing negatively affect the psyche of their kids. I think that it only logical that such an act would have an effect on young children. It is a weird lifestyle and type of a social behavior.