As far as the frequency goes - if you're used to training legs multiple times a week (2-3) you can even do them 5 times! I had a problem with my elbow once and for about two weeks all I did were back squats supersetted very light, high rep pulldowns (to help elbow recovery). I may have done some leg curls/extensions at some point too, but I'm not sure. This was done 5 times a week.
Obviously I didn't go crazy with the volume or intensity, but I didn't approach any workout as a light one, I just tried to do the most volume and weight while being able to keep the frequency up.
It definitely didn't hurt, and it gave me time to work on my form a bit and get used to my working weight at the time.
I didn't try to structure it as a program. My attitude was more like "This is what I can't do. This is what I can. Let's do as much of what I can do and do all that I can to be able to do what I now can't do soon." (Say that fast 10 times).
If that stingray allows you to do front squats I would use them as the focus for the 1-2 weeks and add whatever assistance work you consider necessary.
But most of all make sure you do everything you can to get your wrist sorted out as well and as soon as possible. I injured my wrist a couple of years ago while playing the guitar (yes, it's possible). I couldn't use my left hand for a couple of weeks. And if I'm not careful it starts hurting again.
Just my 2 cents. I hope your wrist gets better soon.