I'd just focus on the overhead clear, as it's the basis of most of the shots. Perhaps do a little re-cap of the serve to begin with. Set 3 cones up , 1 about half way down the court, the 2nd 3/4 back and the 3rd at the back of the court. Give them 6 shots each working in pairs, with either 1, 2 or 3 points, depending on how far the shuttle travels in relation to the cones. Have a worksheet for them to record their scores, and put a simple key at the bottom that explains what scores relate to what NC levels. Then you could perhaps differentiate the future tasks in the lesson depending on their scores, so they are all working on different activities. Have a few peer assessment sheets ready for any non-participants.