This is a great question, @richardsmith. I agree with @johngraves: I think we want to encourage a culture of just getting out there and doing it.
One of the great benefits of the beginning of a new community is that we can explore and try new things. Invariably the first attempt is never perfect, but we learn and proceed from there onwards. Fortunately we are seeing lots of people getting involved running Think Tanks (such as @johngraves, @danrussell, @nicefishfilms, @TrishMcCarty, and @docgee) who I know would be happy to answer questions.
I admire you not wanting to take on too many things, so I would recommend you team up with a few other people to put together a Think Tank in your area. I actually think doing this will be motivating for you: you will get to meet up and hang out with other community members, which in my experience, is always motivating and fun.
I think reaching out to other local groups makes perfect sense. Think Tanks are not designed to replace TEDx - TEDx events are kind of like a dinner party...people get together to see some interesting content and then go home. Think Tanks are designed to be more emcompassing...that they communicate and collaborate in-between meetings and that meetings are not presentations, but also include collaborative discussions about how we can practically solve problems. Make sense?
Just let us know, @richardsmith, if there is anything we can do to help and thanks for all of your efforts!