Call Walt at (281) 664-1690. Walt has been running Walt's shuttle service to help prevent drunk driving in Northwest Houston for years. He is a great guy and advocate of this sort of thing. I'm sure he would be happy to share some of his thoughts and experience with you about getting people to and from bars.
walt-inc.com/
A couple of other items to consider:
1. In the age of Uber and Lyft, it is so easy and inexpensive to avoid driving your service will need to be competitive. Turning the evening into a resident event is a possibility, but you need to be very careful about liability.
2. Because of insurance costs and liability concerns, contracting to a third-party is something I would strongly consider.