Rainbow Rice Garden for Play: Measure rice cups) and put it in a Ziploc bag with about of food coloring or liquid water colors (works great!) and 3 T of rubbing alcohol. mix the rice in the bags to spread the color.
DIY Sand and Rock Box by FSPDT. Gdjk -> made this with toilet rolls (aka tunnels) and moon sand instead of play sand. My son loved playing with it. The moon sand cleans up nicely indoors but play sand will be easier to play with when using the small cars.
How to install a baby gate without drilling into the wooden stair banisters. Cut a couple of to the height of the banister, paint,and secure with heavy zip ties. Then just add the baby gate hardware to the new piece of wood.