Oh Michelle, I wanted to add one quick thing. I'm not surprised to hear your kitties wait, patiently, for Pengy to be done playing. We've experienced the same thing with Ming Loy. Her back leg and hip muscles don't work very well, and she can't walk very far before falling over. I joked a few weeks after adopting her that we should have named her "thumpy" - well - you sure know why, lol! She can't jump well, but she can climb. But she can't climb back down - so those really loud THUMPS used to terrify us, but they don't seem to hurt her. She thumps up and down the stairs - incredibly rapidly! And she "thumps" into everything - mostly the floor. But it clearly doesn't hurt her. In fact, like Pengy, she seems quite unphased by her handicap.
She quickly developed the habit of walking from object to object - that way she stays propped up. And she'll use us and the other cats as one of her "prop objects." The first time we saw her do it, Shelly clearly looked a little taken aback - but he didn't object. In fact, all of the cats seemed to accept her oddity this way (except for Spooky, but she always takes months longer than anyone else to be OK with a newbie). And, like your gang, they wait for her to play before they battle it out for possession of the wand toy.
So... I really think they do understand she's handicapped. It's the only thing that explains our kitties' behavior towards Ming Loy!