Thanks.  I will do my best to stay within the guidelines.  I would still like to offer free admission though to build traffic (and capture the recipients' email addresses, though that benefit to us is not clear from the ad).

I think this promotes our involvement, not the event:

Visit our booth at TI Flea.
Learn the island's history.  For
free admission ($3 valule) go to
treasureislandmuseum.org

How worried should I be that if Google disagrees, our account will be terminated? 

If the ad is just disapproved that would be reasonable and helpful, but I don't want to risk our account.