Hi, I just found out about fish extenders and I would like to learn more. I have 3 young teenagers (13, 15, 15) and they are looking forward to the trip. Can anyone tell me what I need to do to enroll in the fish extender? What type of things can I get to put in it? how often? is it every day? do you chose a family to give to or is it random? It sounds like so much fun for the kids! Thank you in advance!