Blount's Clam Shack always serves beer and wine - it is on their online menu, so there would be no reason expect it to be an area where one would not be exposed to adults consuming alcohol. If parents want to avoid that, they should avoid the clam shack entirely, on any given day, not just during the beer tasting.
I would expect there to be signage in the area of the tasting that would alert concerned parents.
Failing that, the admission fee would also be a clue. This isn't rocket science.
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