ok, update
Problem solved for the most part. I've managed to book the 5 adult lessons for 11:30 on the 18th of November! Unfortunately I was unable to get a child lesson on the same day, and couldn't arrange any other day where we would all be able to ski/board and take lessons at the same time.
Mixitup, I'm sorry, and need you to pass that on to your kid too... I hope this doesn't mean you can't now make it, but if it does, fully understandable!