how old are the kids?
ive taught dyeing before to 5 year olds- pretty cool- they need major plastic protection :lol:
i'd be leery about teaching them real batik - because it involves hot melted wax and it burns a lot when you get it on your skin.
Dharma trading makes a good seaweed based resist that imitates wax well called InkoResist that washes out with water- the only thing is you cant dunk the piece in- you have to surface apply the dye by paintbrush or squeezie bottle....
.... the resist takes a whole day to harden before you can move to the next step though.
ive heard of people using elmers blue washable gel glue as resist as well