This job can involve one of the kids' favorite gadgets: a pair of binoculars. The spotter scans the water and shoreline to pick out marker numbers, buoys, boat traffic, debris, beacons and other landmarks. Visit a site such as fish4fun.com, and help them learn what each buoy/marker signifies. (Example: A "nun buoy" marks the left side of the channel leaving a harbor; it's red with even numbers.)
Unless you've got Al Roker on speed dial, deputize a child to help check current and expected weather conditions via the NOAA broadcast on the VHF radio. Consider having them print a forecast from weather.com before the trip, and then to watch the sky for danger signs once you've embarked.