You spend one day in low loop (Old failthful, Lake yellowstone) and one day in up loop (Mammoth and Canyan). Since it's summer, the sunset will be after 9:30pm so you have enough time to visit the most points.
One thing important to arrange your schedule: The drive from Salt Lake Airport to Grand Teton or Yellowstone is 6-7 hours. Don't miss your flight.
Also book the hotel ASAP since it's hot season.