"Bunny Tails" (Lagurus ovatum)! It's a great, easy to grow annual grass, and the seedheads are fascinatingly tactile. Buy plants or seeds once, and collect the seeds in fall, and you can grow them every year. They germinate easily, and grow fast to 2-3' tall to the seedheads.

Donn's idea is excellent. I make & sell dried arrangements out of grasses, etc, and when attending craft fairs I find kids like to touch. To stop them from mangling my creations, I make up small bouquets of bunny tails and give them out to the kids who pass by. They love them (and leave the rest of the stuff alone).

'Moundry' Fountain Grass has big fuzzy inflourences... I always liked those fuzzy types when I was a kid, fun to tickle with... other types of Fountain Grass also, and there also is a "Little Bunny" isn't there to go with that theme

Miscanthus 'Giganteus' and Arundo donax grow really fast and tall... i find those interesting on my juvenile side thou maybe a little girl wouldn't...as well as Giant Sunflowers which I always assume should be a must for a kid gardner.

Thank you for the suggestions - I especially like the "Bunny Tails" - even though I'm always trying to keep the real bunnies OUT of my yard!

My kids potted up some Juncus spiralis after seeing its strange corkscrew habit. They really thought it was cool. We put the pots into a water filled cement basin in the yard.

And what kid doesn't love water? Any plants/grasses in a water feature adds a real extra element that kids love.

Grass-like plants could include Juncus, Acorus, Cyperus. Lots of grasses work as marginals or pondside plantings. Grasses are really enhanced when reflecting off nearby water.