A note about the phrase "non-toxic."
Many things that are marketed to children are technically "non-toxic," but the definition has to do with a very specific number: how many rats die when fed or exposed to the product within a certain period of time. If the number is relatively low (NOT ZERO), they can stamp "non-toxic" on it and parents think it's perfectly safe to use. Google "LD50" and you'll learn something about it, or go to healthychild dot org, where I've learned a whole hell of a lot about the everyday chemical exposures that we are subjected to that over the LONG run are probably contributing to the rates of cancer and reproductive abnormalities, among many other maladies, in our country.
Remember that ordinary crayons are made of paraffin, which is a petroleum (oil) product. Do you want your kid handling and mouthing something made of petroleum? We make gasoline out of petroleum, and benzene, and other really nasty stuff. And if you've had a chemistry class, well... not too smart to let your kids chew on it, if you ask me.
That's why these soy wax candles are such an amazing idea. The only problem is that if they drop on the floor, they shatter much more easily than your traditional yellow-box mainstream petroleum crayons. So I would save them for an older kid who's not dropping their crayons all the time, like my little one does! A great product for older kids (as in, older than toddlers).