In a business context, I suggest you use the ordinary practice that other pharmacists would use in a similar situation. If they would generally call each other by first names, I suggest you do the same. Calling each other "Dad" or "Son" in the workplace focuses on your family relationship more than your identity as co-workers and professionals. If there are other professional peers in the workplace who can't call the boss "Dad", it puts them in a less favorable position. It's usually a good idea to keep business interactions within the business, and save family interactionsfor evenings or weekends.
Good luck, Dr. Ellen