Scuba Brad:
I'm with Catherine....................you could take them and their spouse or "special other". It could be a REALLY nice dinner or lunch. Make them feel appreciated because they ARE. Having said all of that.......frankly most of the students earn tons more than their instructors...........so hey a buck or two would kill them.
Happy Dining errrr Diving
Both you and Catherine hit on an option I'm torn on... dinner, lunch, drinks, etc. Sometimes it's nice, others it's really more of an inconvenience. I would think if you know your instructor is single and has absolutely nothing to do later, then it might be appropriate. Married, other obligations? At that point, who knows.
I used to get lots of offers for dinner and such - I lived an hour away, have a hard working wife an hour away who doesn't want to kill 2 hours driving into town for dinner, our schedules didn't match so the 2 hours a day we actually get to see each other (sometimes) alone was valued, often I had to work the evening job, so we'd go a few days at a time without seeing each other awake....blah, blah, blah.... anyway, there were numerous times the offer was extremely inconvenient and I had to politely refuse. I think maybe in 4 years I had one or two persons say, well gosh, I still really appreciated your efforts, here's something, do something nice for you and your wife or buy yourself a beer when you have time. I'd have been way ahead of the game if I was given an 85 cent tip every time I couldn't come join them.
I've had people out of the blue give me alcohol without asking, worked for me back in the day, but I actually do know a few "recovering" instructors who definitely do not want or need such items.
It sounds wrong, but cash always works as a tip, anything else, make sure it'll work for the insturctor/DM or whoever.
later,