Adults should discuss what is in front of them as proof of the Earth's orbital motion along with the fundamentals of timekeeping is tied up with the change in position of the stars relative to the orbital plane and the stationary Sun, at least for the purpose of determining the actual loops of the faster moving Venus and Mercury.

It is why Tycho couldn't accept the reasoning of Copernicus as the stellar background references require two separate treatments, one where the stars don't move for the slower planets as the faster Earth overtakes them -

https://apod.nasa.gov/apod/ap120809.html

The faster moving Venus and Mercury require a separate reference system where the stars change their position to the central Sun (Earth's orbital motion) along with the individual motions of the faster planets. The phases are not so much restrictions as they prevent those planets from any sense of illusory loops.

Give it a go and hammer out the solution acceptable for the wider public.