For example in a family meeting, subtle action-oriented questions like "How could we get it started?" or "Who is going to do what?" or "Who could be responsible for centralizing updates around this issue?", and so on, can go a long way to introduce the benefits of a GTD approach without requiring them to master the methodology.
In summary I would say that the MINDSET goes far, even without any formal implementation.
Goncalo Gil Mata