I would suggest Hosta will be toxic to your torts. Have a look at http://www.dr-dan.com/newpage16.htm for a short list of toxic plants to many pets.

Red Foots are like Yellow foots will eat or try to eat anything in their pens. Personally I would keep Hosta plants well away from my torts and instead would grow a large plantains or some other Tortoise friendly/food plant – See the list at this site http://www.turtlestuff.com/foodplantlists.html or http://www.tlady.clara.net/TortGuide/Diet.htm

Good luck in finding a Tort friendly plant for their pen.