Monument Circle is always a safe bet. A Star Bucks in on the Circle, so potty and drink/snack breaks are moments away. Just walk around the Circle a few times, and walk on the Monument. Plenty of changeover in people and things happening.. Parking on the Circle will take 10min or more... but, that is where you want to park.
White River Park, near the Museums on HWY 40 (Washington Street).
Pick a busy street and park, and walk in a 2 block area up one side, and down the other.
Indianapolis Zoo for large animal photos
The Botanical Gardens (next to the Zoo) for plants, butterflies, birds