I have made several "lap" quilts for those at nursing homes. An appropriate size should at most 44" wide. You get too much larger, and they will overflow onto the wheel area and get caught. Sometimes, you can make them wider, but you have to be specific to the recipient nursing home that they give it to someone who is overweight or in some otherway would need a wider quilt. We just finished several at club that were 44 x 57. Plenty long enough to cover the legs and then fold over into the lap.
Some things to be careful for nursing home quilts:
All laundry is washed in piping hot water with purex. Sometimes they add a chemical to remove food/waste stains. Most of the time, it will make colors fade a/o bleed. The problems you run into is also shrinkage, even if you pre-washed. They use the same laundry treatment for each and every load. Quilts will not be treated any different than regular clothing, blankets or undergarments.
Also, I have found that fleece will work well under these washing guidelines. I made my mother a no-sew fleece throw about 5 years before her death. She had it on every time I visited, but I thought she only had it when I came to visit. Turns out, it was her favorite blanket and she had to had it on every day, except when it was in the laundry. Also, I thought my family was taking care of it's laundering process. Oh no, the home washed it just like they wash everything else. It only shrank just a tiny bit the first time it washed. After that, it was great. When she passed away, it was returned to me. It is in excellent condition. It really lasted a long time and it has withstood a lot of abuse at the laundry department.
Just my two cents. I just hate to see so much time going into a quilt only to see it ruined by the professional laundry junk they use.
Sometimes, blankets aren't needed as much as bibs are...adult bibs. But those can be harder to make.
M