For this task, I thought a musical activity might be interesting. This task is an extension to the notation taught to junior primary children- the old “ti-ti ta” rhythm reading system.
In this task, students would be given a number of symbols representing each of the specific notes (ie a star for a quarter note, or “ta”, a circle for ti-ti, etc). They would use these symbols to construct a rhythm (encoding). Students can then share their rhythms with other students who will preform them (decoding).
Alternatively, to simplify the activity, the symbols could be used to represent an action, for example a stomp or a clap and be encoded and decoded by the children.