Draw a middle circle on the left. You can even draw the solar system to scale by reducing the distances between the planets and the sun. Once they understand how easy it is to apply these ovals around the center, they can draw them anywhere on the paper, at any scale they want. Then draw 8 circles to the right of the Sun so you have 1 for every planet in the solar system, including Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
If you know what colors you want to use in your drawing, you can also experiment with different art media.
How to draw a plant step by step?