My cats usually have grass available to them and they greatly enjoy it. The ones sold commercially are generally too tall - I cut them down to about 2 to 3 inches. [Long story -- emergency vet trip due to 6" blade of grass mis-swallowed. Grrr.]

Cassy, in particular, runs amuck when new grass come in. He either holds it to his face by wrapping his arms around it, or holds my hand holding the container while he gnaws. SOOOO cute.

I'm told the reason that cats prefer to puke on carpet [sorry to be crude ] is that they like to sink their claws into something when they're getting sick -- it helps them feel more stablized, apparently.

Good luck with your fur-babies. If they're like mine they'll LOVE cat grass.