While we're on the farm topic, how can you incorporate art into a farm discussion? Paint with vehicles you might find on the farm and use "farm" colors. Creating curated activities is often as simple as choosing the right colors and materials to evoke a place or time.
We did this activity in the fall, so our farm colors were brown, yellow, green, and red. Luckily, we also had a tractor on hand, but you can use whatever vehicles you have. Then after, have a car wash for those dirty cars!
This is an open invitation, so whatever your child comes up with is perfect! You provide the materials and then they create the art, no pressure, no expectations. Just like preschool!