It's great that you're trying to get something going. Just don't think that being a club member means "active." There are plenty of clubs of various sorts with only a few (or one) regular participant and scads of names on a list that don't show up. Even dues-paying members may not actually go out.
You might want to start with an informal group, such as the Facebook option someone else mentioned. Or you can start a Meetup or Yahoo group without going through the hassle of bureaucratic requirements. Also consider what your legal liabilities might be. I'm not saying this to scare you into joining the herd of ACA clubs; you can take out your own umbrella liability insurance instead. Better yet, make it only a gathering of like-minded equals, nothing that could be construed as simulating a commercial outfitter's role. Look up "Common Adventure Model" and see if that fits what you are trying to do.
Another option would be to use this board to ask for interest in a specific outing, but rather than trust others to show up without any kind of preamble, maybe you could all meet for coffee first on a different day. Then get to know each other a little bit first before committing to a shuttle, a full day out, etc. THEN you might have a better chance of people following through on what they say. They're not anonymous anymore. Personally, I would never count on some stranger to show up if I had to depend on them for logistical reasons. But I see lots of posts in here where anybody with a car is welcome to hop on for the outing...strikes me as very risky in several ways.