I agree with the top down approach, we get plenty of advertising campaigns around speeding, driving tired, drink driving, drug driving and using mobiles. These are all part of the rules of the road which, assuming a licence is held, a driver should already know. Yet I can't remember any campaign that explained the rights of other road users. Again drivers are meant to know these but my experiences would indicate otherwise. As would a quick read of 'news' articles, comments sections, a gazillion forums and the stuff shouted at cyclists by random drivers.
Re the OP and riding two abreast, I do this most frequently if out teaching one of the boys how to ride on the road. They'd normally be ahead of me and I'll be encouraging them to move out from the gutter. I think they're all heartily sick of me telling them of the dangers of pedal strike on the kerb and the problems around gutter riding. To shield them I would normally be in the middle of the lane and I've never had abuse from a driver over this, in fact quite the opposite. I'm sure this is partly due to the more residential roads being ridden but swap my son for an adult rider and I bet I'd get abuse.
Personally I find riding side by side with someone far superior to single file.