Why not, Jo?
I can imagine the Dutch being so good at this. As long as it's not too "corporate", as with a lot of these in the US. By that I mean, it has to be fun and not po-faced and evangelistic.
Back in the day, these kinds of retreats tended to be loopy affairs, when everyone believed that all you needed to change the world, was a guitar and a sack of brown rice.
This looks as safe as you can get. Not like the old days when mushrooms were tame, and people really wanted acid. I can remember times when some div would do what Mamya was talking about. Spiked drinks, and the severely spaced-out having to be talked down.
Compared to the old hippy days, this is probably quite clinical.
Have a good trip.......... nudge nudge ;o)