Is this for yourself, or are you a yoga teacher with a student in a wheelchair? There are lots of sites that have suggestions for doing Yoga in a wheelchair, or even just in a chair. Here are a few that a quick search came up with for me:
Wheelchair Yoga
Yoga for Individuals with Disabilities
Chair sun salutations
So, yes - being in a wheelchair is no impediment to doing yoga. I know of one yoga teacher who was quite popular and experienced, who had a skiing accident and now teaches from her wheelchair. (You can check out Mary Jo Fetterly's story
here.)
Teaching Yin Yoga to someone in a wheelchair is also possible: just remember the basic principles: 1) come to an edge, 2) become still, 3) hold for time. The edge is where the student feels some stress. You can creatively work with the student to find postures where a stress is felt and let them pay attention and linger.
I sometimes have a student who comes to class in his wheelchair. He is highly functional despite the chair. He gets down on the floor easily, uses his arms to move his body into and out of postures and says he feels great afterwards. In Yin Yoga, since we don't do any standing postures, this works well for him. But, obviously there will be other students not so functional, and you will have to tailor the practice to them. Maybe they can't even get down on the floor, but they can still do some upper body work.
Practice with attention and intention and let us know how it goes!
Good luck,
Bernie