Yesterday I tried the "Challenge Grand Prix" on the little track.
For only 45 euros, you have 10 minutes of free trials, 10 minutes of time trials and a 20 minutes race.
But we can drive longer and even, if we are enough numerous, organise team race with a change of pilots. The system is you pay by kart, not by pilot.
The little track is 900m and 6m-large, the competition one a few less than 1200m and 8m-large.
Comments on the litttle track: not a lot of spots to overtake "properly"

, good curves, a funny bridge,..., maybe it could be enough for a first try (could be completed by a few runs on the competition one).
Now I wait for your advice and ideas and interests !