Art that is easy and fun to do with small children: paint your hand and make e.g. roosters or fish. Why not a butterfly using both hands or a caterpillar (many hand prints fingers down in a row) too? Makes fun cards!
Last Christmas I wanted to make Christmas cards together with my kids My son was then only about a year, so we ended up doing snow men with little fingers.
Earlier art: on the left my daughter’s idea of painting with water colours when she was about 2. On the right are the pictures my husband did with both kids, the older ones hand and foot prints at less than 2 yrs on the younger ones at about 6 months.