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."
Geum triflorum (Prairie Smoke) is one of the most stunning and longest lasting prairie perennials, with unmistakable feathery silver and pink seedheads in mid-spring. It is a soft, hairy plant growing typically to 16" tall with fern-like leaves. It prefers full sun and average to dry soil. It is drought tolerant once established, grows in sand, gravel and rock gardens. It spreads by rhizomes and can be naturalized to form an interesting ground cover.
Moss Phlox (Phlox subulata) is a richly flowering, clump-forming phlox that stays green in both summer & winter. In spring these plants produce innumerable crimson & white flowers that attract butterflies. These Phlox like to be planted in full sunshine.