uneeq,
As far as Maris Ayin, these guys going to this waterfront treif restaurant is no different than if you saw a Yid sitting down in McDonald’s drinking soda.
There is no difference between this restaurant and a McDoanld’s.
Just because a viewer should be dan lkaf zchus, does not excuse the party from maris ayin. Otherwise you could say there is no such thing as MA (obviously incorrect) since everyone should always be DLZ.