Not sure if you are thinking more formal training, or more of an exploration to see if they have skill or liking for something.
If it is more exploration I suggest you make it a family project. Make salt clay together and sculpt something, maybe even one item, but can be one each. At crafts 200o you can get paint by numbers and something like pencil by numbers, plus many other crafts. But also you can get poster board and cut out pictures from magazines and make a montage. You can do a “what I like” one, or some other theme to help them get a focus on what to do.
Use craft (popsicle) sticks to make a flat “canvas” and paint, or what is more fun is to gather a box of small things like stray buttons, broken jewelry, caps, string, or any other small trinket and glue them on the surface, hang with a piece of yarn and you have some cool modern art.
Drawing, and painting for that matter, is all about training your hands to do repeated forms. Most art is all of similar curves and shapes, for instance making a perfect circle without an aid. Harder is making straight lines, or increasing the difficulty to parallel lines with consistent equal distance and straight. The second part of “learning” is pressure, how hard to press the pencil or brush.
My personal thinking is to make it a family fun time more than something to be learned, because if it is fun you learn more.
With my kids we did, and still do when we all have time, sit down and take a small picture, drawing and use a sheet of typing paper to redraw it larger. Usually the original is only a couple of inches and expands to the new one many times larger. In the transfer the person’s style changes it to be their own. My son and daughter prefer anime, while I do more advanced things, but it is still just family fun time. For us, those are just paper and pencil, nothing fancy. You can get about anything you want off the internet to use as material, but suggest that you convert to grayscale when printing to avoid color transfer issues.
Another fun one. Take sheets of typing paper and blob splotches or streaks of wet water colors (kids paint set works) and bend it in half without creasing to spread the blotches. Leave a lot of white. When dry take pencils and make things from the blotches like finding images in the clouds. I think my kids started with that. You know... “hey, look, that blob looks like a dog” and draw over it to make it a dog.
I think the most important lesson of art is “there is no such thing as a mistake” if you boo boo just keep going and make it different.
So, unless you have a child with real potential that needs formal training, then make if a family fun thing instead. Everyone will benefit.