I'd suggest a 2 segment trip, medium length segment (say 1.5-2 hours) runway change on taxi out with takeoff in rainy conditions (see if they apply an optional V1 computation to give a margin of performance). If you want some "entertainment" have the departure be out of an airport that is over flat terrain near sea level and on climbout they get an incorrect TAWS warning climbing through 5000' or so. Then uneventful until level off at initial cruise altitude give it a few minutes before they start getting rocked by moderate turbulence, inevitably they'll query for what is smooth, and say every altitude above FL280 is reporting moderate turbulence, see what they do. On approach to first destination a storm moves over the field (part of a front), see if they account for this in their approach (wx ok though, 4 miles vis or so and 1000 ft ceiling.
2nd segment is departure from this same airport on a short segment (30 mins), see if they work ahead here and get themselves set up to go directly from departure to approach without having to shuffle through all their stuff wasting valuable time. With an uneventful cruise portion, on initial descent encounter of oncoming traffic not reported by ATC (see if they even bother to tell the controller about it). On approach there is traffic ahead which flies their approach slower than usual (again, see if they can adjust on the go), then the aircraft ahead experiences a gear failure on the only runway at the airport. Since wx was CAVU at the field your reserves are minimal and nearby airports with runways that have a "more than sufficient" length have low wx (300-400 OVC 1/2 mile), airports with runways at the limit for the landing performance manual are much better (1500 SCT 6+ miles), see how they deal with that.