what time does the airport shuttle pick-up until? We are arriving on a week night a 9pm? Also the next day what would be the most economical way to get to Enteprise car rental at 515 Donnelson Pike?

You should be able to call about shuttle times, but I believe they will pick you up anytime. If it's within 5 miles of the hotel, enterprise will pick you up.

Uber 1 mile to enterprise and 2 to Preston.

Call Enterprise, they should pick you up free. Also, tell the front desk in advance, and they will do their best to accommodate. We had to fly out early and they had the shuttle ready at 0545.