I have nothing to add reagrding secret web sites, but do have some experience with AROC conventions; involved in the planning of three: 1981, 1990, 2007.
My personal views:
Do not set out with the attittude to do anything bigger or better than what was done before. Those comparisons are full of traps, so just plan for everyone to have fun.
What we did do was put a core group together and worked like hell to make the most of what we had at hand.
That means that if you have a professional witer or PR
person in the group, use that to your advantage. If there is a 1923 RL in the Chicago Science and Industry Museum (hint, hint, hint) look into options of using the car or museum for an event. With a little asking and prodding, you might find a member who suddenly spouts 'Oh yeah, my sister is the exhibit curator at that museum.'
Feature your strengths, both those of your members and the convention area. Every area is unique, and as Eric noted, the majority of members will be coming as tourists.
The GTA demo laps at Waterford Hills was not in our plans until I looked at the registration list and counted seven GTAs. Only then did I begin mailing to all the GTA owners in the club, sending a letter and registration form to each one, using the seven we had as the enticement to make it twelve GTAs registered. Like I said, it helps to be aware of what you have.
Not everything can be an area of strength (for instance, Detroit never does rallies). Then either do some creative substitution (we had a combination gimmick rally and gossipy tour near the hotel), or keep it simple, or farm the job to someone who is really good at it.
I have strong opinions of what is works and will not work at a convention. Sometimes Eric and I had opposing opnions. In the end, that worked to the Motor City Alfa's benefit.
Motor City Alfa co-chair