The Charles in question is a poor candidate for a polyamorous relationship. It's obvious he has a lot of issues to work out about his own needs and his marriage and he's trying to fix them by running to a new relationship. That is a very bad idea. Regardless of the very real problem of strongarming his wife to enter this relationship scenerio, Charles is doomed to failure as he will just take his current problems into his new format without solving them. Even if the wife were willing and enthusiastic, I'd discourage them from taking this path before getting considerable professional counseling first.
The whole conflict with Charles and his wife is a separate issue than whether polyamorous relationships can work and be healthy.
My wife and I, together now eighteen years, started dating as high-school sweethearts. We lost our viriginity to each other and were each other's only sexual or amorous experience. Then four years ago we realized that most of our friends were in long-term polyamorous relationships and contrary to our notions of polyamory as irresponsible swinging we saw that these people were truly committed to each other and were raising healthy kids. They were the most responsible people we knew, taking care of commitments and obligations, covering every health issue, nuturing each other's growth. In short, we saw that the notion could work. We also did some introspection and long discussion and decided that this well reflected our personal notions of love as a plentiful personal resource that could be shared beyond a single partner.
Now my wife has a boyfriend, a very nice man with an adolescent son whom I respect and trust to treat my wife's emotional needs with gentleness and consideration. When she goes to spend a weekend with him don't feel jealousy -- I know too well that we are truly each other's primary partner and mate so I feel no danger that she will leave me for him. I feel gratified and almost jubilant at the thought that my wife is getting a chance to experience the joys of discovering a new love and exploring new romantic terrain. When she gets home we chat in bed about her date, like two schoolgirls giggling under the covers, sharing the experience between us and bringing what she's learned into our relationship.
I also have a secondary relationship. She's engaged to another man, a deeply intelligent fellow whom I've been glad to call a friend for a number of years. She's a good friend to my wife, in fact my wife first encouraged me to date her, and they often go shopping or the like. To those who say polyamory is all about sex, I can say that I am romantically devoted to this woman despite the fact that due to her current pursuit of an enginerring degree, a 100-mile separation, and the time she needs to spend with her fiance, we've only been sexually involved once in nearly eighteen months. She broadens my perspective on life and enriches my soul in many ways other than sexual. When circumstances permit we'll resume a more active sexual life, but that will be just another course in the banquet of our relationship.
There are healthy poly relationships and there is Charles' situation. I'd advise his wife to take a deep look at whether she wishes to remain with a man who is obviously unwilling to heal a fractured marriage and is seeking a shortcut in extramarital sexual satisfaction.