I am powering the Arduino with it as well. When I was using the Every, I had problems with the display if the voltage was different so I have kept it like that. I had the same issue with the display while coming to Vin, dont know why, therefore I have used the step down and solved it like this. Maybe with the Nano classic it would be different but I had this already in place and thus only changed the Arduino from the shield,
br. Tomas