This problem requires children to work in a systematic way to find all possibilities.

How will you record what you're doing?

How will you make sure you find all the possibilities?

The problem could be simplified to just two elves, then three elves, so that children become confident with a particular system before there are too many possibilities. You could ask learners to record each possibility on a separate piece of paper so that a system can be imposed afterwards and gaps can be filled.