Ideally you would want to practice the Mindfulness MBSR core practices for the 30 - 45 minutes rather than breaking it up with different practices. Our recordings are 45 minutes for the Body Scan and 30 minutes for other practices so they will support you.
I would also recommend that you just sit with the intention of just sitting, moving from doing to being, using the anchor of your breath to open to your experience in the moment. There is no need to strive towards doing better, rather have a beginners mind to being with what it there be it pleasant, unpleasant or neutral. When you find the mind has wandered to body sensations, thoughts or emotions (and it will, that's what minds do!) just notice where it has gone and then choosing to return your awareness to the anchor of your breath. You may need to do this many many times and that's OK you are strengthening your mindfulness muscle!