Ginny, as a small business owner I want to make a few suggestions. First, I was able to work light duty after the surgical recovery (radical neck dissection, tonsillectomy) which was about 2 weeks. I was also able to work light duty during my radiation treatments and was able to drive as well. Fatigue and pain especially the last weeks of radiation were a problem. I did not have chemo and that will make things worse. You might be able to do your work although I wouldn't recommend it. The mental stress and pain medications might make it a liability for you.
I have a suggestion for you that may sound contrary. Is there a competing company in the area that you might ask to take over for the period of your treatments and recovery? This may not work but I heard of a company that came to the aid of their competition in this time of need. Naturally you might need some legal guidance, but maybe it is worth consideration. (they might also be perfect buyers after time as well)

I truly needed to off load all stress. I really believe it complicates healing. This is a time for you to focus on you. Everything else will take care of itself. If necessary, seek legal advice about the business and what to do in case you cannot return to work. Get your personal legal papers up to date at the same time.

lastly, see the social security office right now. You may qualify for disability with SSDI. I did not do this and have great regrets about it (I never even thought about it). There are time issues before you can qualify. Check into it NOW don't wait and don't be too proud. If you had your own disability coverage use it too.