I agree with Kneafseym, if you go into too much detail I think some eyes may glaze over for the first timers. Sounds like you'll have one real first mate, he will be your go to guy and can help instruct grabbing mooring balls and setting up dock lines and fenders once in the islands. Safety on the boat would be my focus, demonstrating a MOB is a good idea so they know what to expect in an emergency. Understanding hazards is important and their extra eyes can help you, lines in the water, where not to be when tacking, securing everything before heading out, alerting of boat traffic, always making sure the Skipper is properly hydrated! Go out and have a great team building day and consider keeping it casual, have them raise/lower the sails, explain points of sail so they understand why you can't always sail straight to your destination, have them assume the helm, they'll be hooked! What boat are you chartering?