I'd like for it to be an event open to any car club, but the initial focus was the "local" club. I'd say anyone with an interest in driving for fun would be invited.
After polling the members it looks like most people would not want to travel more than 500miles, including the caching event. That's why I picked 250 as the mileage
I'd like to expand it to include other car clubs eventually, but I'd like to start on a small scale first and then expand.
Although gas might be expensive, we don't drive for transportation in these events: we spend this money to have some fun, just like some people spend money to play golf or whatever.