Hey S-Dog
I built the largest independent scuba club in the Pacific Northwest (Moss Bay Divers)
http://www.mossbaydiveclub.org/portal/index.php with over 500 members. Additionally I have begun a consulting company that specializes in creating dive clubs for dive centers and have been actively working at this with shops from all over the world.
In my Opinion
Liability is always and issue and you can't skirt it. There are two routes you can go.
1. Stay completely away from calling yourself a club at all, ever, anytime. this will help distance you from any association with Responsibility or Stewardship for extended members of the group. (your personal dive buddy will always be a different story)
2. Do it right and form a legal club as defined by the laws of your state. Run it properly and make sure you get a good liability release signed by each member preferably one for each year and in addition one before each day of diving.
Not charging for membership does not limit your liability and in fact could possibly increase it. Implied is a term you need to worry about because by simply offering a diving opportunity you are implying that certain outcomes will happen and if they don't...
I have yet to find an insurance company that would write a policy for a dive club so that's out unless you know of one and if you do I would sure appreciate it if you would let me know what company that is.
What I am saying is that this could be a much bigger "fish" than what you want it to be so if you are not really serious about wanting to "fight it all the way to the boat" you may want to just go diving and forget about he club designation.
Whatever route you choose I wish the best for you