If you're looking for a way to get children interested (and some adults!) in growing seeds, how about this for a fun project?
All you need are some nylon pop socks, compost and grass seeds - permanent markers, felt & wool optional.
Just place a handful of grass seed into the toe of the pop sock then add compost to whatever size head you desire. Once full, tie a knot in the loose end and snip off the excess fabric.
Place on a dish and water until the compost is moist, then just add water as required. The grass will keep growing for weeks - months even - so can be snipped and styled frequently.