Many times parents have told me of a child who loves to draw. They usually ask if I teach children (no) or if there's another teacher I could recommend. I think my stock answer surprises them as I explain the following.
Children's art is often far better than that of a novice adult. It is creative expression in the purest form. They know nothing about perspective, color harmony, or any of those other grown-up theoretical considerations. Little children are not mentally or emotionally ready for them. Academic lessons may even thwart their artistic growth and potential.
Once we adults understand and control the picture-making ingredients, essential to creating illusions of space, form, depth, light, shadow, etc., that other adults expect, we need to return to our child within, adapting the theoretical to our own innocent, carefree, unencumbered (matured) pure expression. That's what it's all about.
To me, the best contribution a Mommy and/or Daddy could make would be to demonstrate genuine interest in everything their children do. Turn off the TV or stereo and disconnect the phone. Make it a special time. Look at their artwork slowly, with them.
Ask questions like, "Tell me about this." Overlook distortions and abstract depictions. NEVER be critical. Ask and listen. When the time is right, make suggestions. Not by critiquing what they've done, but by expanding their options-awareness. For example, imagine they've shown you their depiction of a duck. It may be quite inaccurate to you, but don't even mention that. Take advantage of a wonderful opportunity. Explain that other birds are different. Show a photo of a goose, swan, egret, or any other fowl. Point out longer legs, a larger body, or a curved beak. Help them develop the habit of being observant and analytical. Allow them to portray the subject in their own unique way. They're doing their best; nothing more should be expected.
Your genuine interest, enthusiasm, and involvement will benefit your children far more than academic lessons from a credentialed art expert. To them you, and only you, are the supreme authority on everything. Appreciate that as an obligatory opportunity (and responsibility) to help them see the world through their own artistic eyes, not yours. They will enjoy their future life far more than those who look but do not see. When your child is ready for formal instruction (so they can visually communicate with those who need explicit, accurate explanations), they'll let you know.