It sounds like Norm is an outgoing extrovert and Tanner is more shy, maybe a little on the introverted side or a little spooky. There is nothing wrong with them being different, and having different comfort levels. I personally would not medicate a dog to try and achieve a different personality. It's OK for Tanner to be different and to not enjoy the same things Norm does. Maybe you could find a behaviorist who could help you with exercises to help Tanner gain more self confidence, and persue that before considering medication.
In Dewey maybe you could take Tanner and Norm both out in the early mornings when people are just strolling around and walking the beach, and in the busy times maybe you and Tanner could have some quiet time wherever you are staying. With the shy greys it can take several years for their self confidence to bloom, and it takes baby steps. Two years is a relatively short amount of time.
There are times that something like Prosac may indeed be the answer, but from your description Tanner just sounds like a shy greyhound who is happier not going out.