First 2 days: focus on assessing your students well and adapting your teaching style to meet their needs. Identify which Unit in your coursebook would best correspond to the actual level of the majority of your students, and start teaching from there.
The rest of week one: teach mostly from the coursebook.
Second week: the coursebook will serve as a resource book to provide the "backbone/outline" of your classes, and you add the "muscles" in the form of your own materials. Gradually, feel free to put together your own classes from scratch.
Assess the true level of your students, meet their needs, and improve their English, i.e. move their active English language skills from point A to point A+ in every lesson.
Please make sure your students are aware of their progress at the end of each class, and at the end of the course.