Amigurumi Tutorial: Nylon Stocking Liner Technique. This will definitely keep the stuffing inside preventing children from pulling it out since they love to poke and pull at their toys http://inskeinasylum.com/questions-and-answers/form-q-a/holey-dc
Mix grass seed in with potting soil. Fill up a nylon. Tie into segments with string to make a 'caterpillar." Soak in water till saturated. Then let the kids spray it with water every day after and watch it grow. When the grass gets "too long" let the kids give it a "haircut."