Cab Sauv Comparison Flight

Like many others, I love to do tastings in which we compare certain varietals side by side with differing regions, classifications, vintages, etc. I’m trying to plan one for Christmas with my in-laws, but unfortunately (for the circumstance) they are strictly a Cabernet Sauvignon and Merlot family. I’m feeling a little stumped in regard to which direction to take this, so I was hopeful that you lovely people had some ideas. Obviously regional comparison seems like the easiest approach, but is it the best? I’m located in Vancouver, BC, so although price point isn’t much of a factor (aiming for <$100 a bottle) my location may make exact bottle recos not feasible. Thank you in advance!