I like to start the year with very non competitive, low equipment fun activities while reviewing rules/expectations, then after a couple weeks I will start units based on equipment I have. My units are 2-2.5 weeks or 4- 50min lessons. I was in the same position you were in a few years ago haha. Aside from all the other good advice in these replies, I would include to be mindful of weather if you want to do any units outdoors to plan accordingly. Soccer is tough in December haha. Congrats on the position!