I want to show the kids how to draw and scribble but markers get sucked on, crayons get eaten, and it generally turns into a mess so I give up and put it all away vowing to try again another time. I've tried a variety of no mess markers that need special paper to draw, but while that's a great thought, the girls just rip up the paper and suck on the pens. Dry erase markers wipe off pretty easily so I was trying that for a while, but I still don't like spending all my time trying to get markers away from mouths.
The one system that's working for me is the Melissa & Doug Water Wow Kit. They have these little brushes that you fill with water and the cardboard pages are generally white with black outlines. As the pages get wet, color is revealed. It takes the pages 5-10 minutes to dry and become white again. Middie Biddie does like sucking on the brushes, but it's just water so it doesn't bother me. When they get older, some of the books have outlines for numbers and letters so they can practice writing.
I don't talk about specific products very often because I hate sounding like an advertisement, but I really like these. I found out about them from another mom in my Moms of Multiples club.