FlowerPower,
There is no right answer regarding whether or not to eat a little nuts, avocado, coconut, or added oil - lets say an ounce of nuts per day or 1 avocado per day. C. Esselstyn says "NO OIL." He says no nuts or avocado if you have heart disease. Many on this board use very strict rules partly because it is easier for them than moderation. McDougall says as much in his videos. I think that he says that he is passionate and can't do moderation (I'm not sure of the exact quotes). Sometimes strict rules are easier to follow than constantly deciding if one more handful is too much. Jeff Novick is pretty clear about nuts and oil, and his popular video is on sale at the moment I think.
http://www.drmcdougall.com/health/shopping/dvds/food-diet/oil-to-nuts/. Fuhrman is more favorable to eating more fatty foods if you want to eat salads and don't like starches, but even he is against adding olive oil:
http://www.drfuhrman.com/faq/question.aspx?sid=16&qindex=8. So, there is a spectrum of advice of from this group of doctors, but non advocate adding oils. You will see that spectrum reflected in comments on this board, although this board is provided by Dr. McDougall.
Campbell is a nutritionist and is concerned with making accurate statements, but he generally doesn't seem as worried about what advice will be most helpful to give people to get them to succeed. I think that he doesn't have the same experience of watching people get confused about nutritional advice as the other docs, and so he doesn't show the same care in giving clear can't be misinterpreted advice.
Adding oil will not help you lose weight. If your husband adds it while cooking, it will make it harder for you. If he adds just a very little, it might not do much if any harm to your family. If they want to eat avocado and nuts, I would not try to stop them. I eat avocado and nuts myself.
Eating chips, fries, vegan cheese, crackers, and other oily processed foods all of the time is another matter. None of the plant doctors is encouraging that. Only you can decide how much of that to eat as you transition to a healthier diet, but they will make it harder to lose weight and will lower the quality of your diet.
FakeCanadian,
If you are confused about what Campbell thinks of eating cheese, then you are in the middle of a huge bout of wishful thinking. Perhaps you missed the part about animal protein in this article or have forgotten how big a point he makes about Casein in his books, speeches, etc.