The modeling wax from Ailefo is organic and food grade, so you can safely pass it on to your little ones. The same with the organic modeling wax from The Wild Harts.
If the children taste the organic modeling wax, nothing happens, but I don't think they will care about the taste :-)
You will also find a selection of modeling beeswax from Stockmar. Note that Stockmar's model beeswax is not certified organic, but instead made from natural beeswax.