I have not tried it nor have I seen anyone do it.
Sounds okay except that your kids will have to ride one handed to do the press to talk. Okay in most situations but it could be dangerous in traffic or on a crowded bike trail. A two way radio is not a bad thing to have in a large group ride where your tweener wants to ride a little independently from the family. We have used it to check where each other is but we stop to use it unless my stoker on the tandem uses it. It generally gets very little use because our oldest can't ride and talk so they don't answer unless they are at a stop.