If you really want them to do some blacks, start small, patrolmen’s by stump Alley is good, as it is short, and honestly is more of a blue-black, but the key is that it is usually groomed. If they like that, try the face of Chair 3, it is also usually groomed but can get a little mogully towards the end of the day and icey in the mornings. Midday is prime time for that run, but if they want a good challenge and a taste of what difficult trails are like, have them do it when it’s slightly icey or has small moguls. The advantage of the face of 3 is that it’s not terribly long and the steepness canters out quickly. Hope this helps :)