Last week we had a play date with a friend at one of the local children's museums. This museum is my personal favorite children's museums - it is usually not over crowded; it is well maintained, and there are lots of volunteers to keep things running smoothly.
Painting the walls in the art space (an enclosed room with glass walls and every surface is paintable).
Fishing and floating boats in the outdoor river.
Looking through the microscope in the science area.