Sweet potatoe plants are so much fun.  It would be a fun project for your kids.  Put tooth pics in the side of the potatoe and place in a tall glass or jar.  I did learn to change the water ever couple days.  When it gets too big for the window seal, transplant into a planter and sit on your porch or even plant in the yard near a fence or make shift trailice to climb up on.  You kids will be able to see it grow each day.