Get them to read the right stuff. If they actually take the time to go through the canon of modern PM work (starting with Lean Startup), they'll probably start

Get them to read the right stuff. If they actually take the time to go through the canon of modern PM work (starting with Lean Startup), they'll probably start seeing sense. As a formerly non-technical person, it's worth pointing out that it's really hard to understand the pain of development if you don't do it. So communicate the tradeoffs: that, they'll get. Say "I don't know" more, and be clear about risks in developing new features. Be open. If they're good managers, they'll respond well, assuming they trust you and not just their own genius (which I think is the danger with Idea Men).