CFI reported landing gear up landing while doing a checkout with a new owner who had no previous complex aircraft experience.

Narrative

I was the CFI doing transition training with a new Mooney pilot. The individual did not have complex time prior to this training and that was an objective to accomplish over a couple of lessons.We spent more than 2 hours going through the airplane's checklist; POH; best practices to fly complex planes; the differences between tachometer only and an engine requiring a manifold pressure gauge as well. We talked about the standard pattern to fly; power settings; where the configuration changes should be made. We then did a very thorough preflight; introducing the new owner to Mooney specific points of interest; risk; and management. We took off and did some air work to familiarize the owner with the plane and demonstrate the edges of its envelope with turns to headings; climbs and descents; slow flight; stalls; steep turns; slips. We went back to the airport of origination and did a full stop landing. We were high and fast and worked on the standard pattern power settings and points where to do the various configuration changes and landed successfully with good usage of the checklist. We taxied back to a different runway and took off. We were coming in for our second landing. Abeam the numbers; I called out fuel pump on; drop the gear; and get into the white arc of the airspeed indicator and drop the first notch of flaps. However; again; we were too high and too fast and that became a distraction. We continued too fast all the way down and we were floating down the runway; which should have been the first indication a configuration issue. I was ambivalent and deciding to go around or not. We still had plenty of runway so I wanted to give the pilot the opportunity to put it down. In retrospect; that would have saved the day but that was not obvious.And; of course; I've played this out in my mind over and over and over again how I missed the normal callouts for gear down. Why I didn't call out 'gear down' at the three points I always do I can only attribute to the distraction of the additional altitude and speed.