There is a lot of feedback on how to do this, but the best way that takes the least time is to hire a professional! Armed with more than pencil and paper, CCA tours engage and enlighten with myriad materials…. And show how to do it on your own. For more info on taking your little one: http://arts.gov/art-works/2014/preparing-children-art-museums
CCA tip: Make it a Child-Directed trip- Ask 
these questions about each piece they are drawn to:
What materials is it made from?
How do you think they did it?
Guess what the artist was thinking when they made it?
What do you like?
What do you not like?
How would you make your own version?
If you’re nervous about bringing more than a pencil & paper, make a list of what your child needs to make their own version, go together to get the supplies and follow it up at home.
Imagine how excited they will get about art. And the interest they will have on their next visit!