Smoking rules in vehicles - from 1 October 2015

I have been looking up if the man is driving, then the son can legally smoke in the car. But if the man is driving with son as passenger, and both are smoking, then the father can be fined because he is carrying a passenger who is under 18.

Touring caravans are exempt providing they are being used as living accommodation (i.e., when sited on a campsite). But what about when the are parked up at a motorway services, or a layby, and the family are resting in the caravan whilst they have a cup of tea?
If the family includes, say, a father and a 17-year-old who smoke, and a 14-year-old, then the father can be fined for smoking in the presence of both his children (2 fines), and the 17-year-old could be fined for smoking in the presence of the 14-year-old.
And, in all probability, the 14-year-old most likely smokes when with his school friends, even if his parents don't know.

We and our immediate families are all non-smokers and I can appreciate the health concerns for younger children, but do the government really need to wrap the law in such tight jargon that even the most caring of parents can innocently step over to the wrong side of the law?