We had rules very similar to Karel's & they worked great. Contrary to her kids, though, ours spent more & more time with they kids as the trip went on. They loved it & we loved hearing about their day every night at dinner & whenever we could catch them throughout the day.
In addition to meeting up at dinner & leaving notes in the cabins & 'popping in on them' at different times, we also would get extra copies of the navigators every night & then we would circle the expected places we believed we would be & they would do the same & all of us had a copy of where the other would be. We basically stuck to our intended schedule & if we didn't, they knew they could find us either at the pool or at the next event.
We tried the 2-way radios, but they didn't work for us & the kids hated lugging them around.