I'm a full time instructor and still work part time at the bedside. I could easily work 4 shifts a month, if I wanted to, even more when I think about how many breaks we have (Spring break, easter, Summer, fall break, Winter, etc.). The burnout in academia is so much less for me that I'm not as tired on my days off and can therefore work back at the bedside (when I'm feeling froggy ).
Since you'll be online, it shouldn't be too difficult. Prior to the students starting, you should already have a plan for the semester so you can begin early on getting prepped. For the next semester, it will be even easier because you should have most of your materials prepared (assuming you're teaching the same courses).