Hi Ole how are things in Norway? I would gladly trade weather with you now.
I'm old fashioned about all beginners. I treat them like Mendez did. They buzz simple songs before they ever pick up the horn. This helps to build some muscle strength and control without adding bad habits. I know that they want to play and will try however if you insist on 20 - 30 minutes of buzzing a player with 1 week of experience will out play anyone elses' 1 month player.
It forces them to learn a closed setting which helps range, tone, and endurance. Let them use buzzing practice after every playing session for a couple of months and you will be shocked at the results.