Well where are you planning on planting them? In side or outdoors? What is the place where you are planning to grow them like (light levels?). These things can really limit, or atleast make it more of a challenge, what you can grow. But I would just get seeds of any edible plant that you think would grow best in the environment and start from there. Good luck
I noticed that in some of Terryo's pictures of Pio's habitat she has Spring Mix growing. You can buy any of the lettuces. There's a broad-leaf seed mixture on Turtlestuff.com and on carolinapetsupply.com. But, any veggie seeds, clover or dichondra would be good. As the vegetable plants grow, the tortoises eat the leaves, and the plants usually never make it to the veggie stage.