I suggest a paper chart, it is fun to spread out and show your guests in the charter party the next day's itinerary (emphasize subject to change, the most dangerous thing for cruising sailboats is a schedule) and if there are any kids on board, each can take a turn "navigating" by tracking your progress from island to island and marking your track on the chart. When you get home, it's fun to relive the trip with the track on the chart and coinciding photos. You can even make copies and distribute to the other guests after you get home.