As the kids and I unpacked the ornaments, we put them into two piles:
1) stuff that can break easily
2) stuff that can be played with and broken under extreme circumstances

Anything in Pile 2 was fair game for the kids to play with until it was placed on the tree.  The sorted through Pile 2, looking for the best treasures to play with before they were placed on the Do Not Touch Christmas Tree.  They each picked out a few and went off in different directions.  After a few minutes, I heard Martin singing to himself, not the Arial refrain that is Sophie's signature song.  Instead - a musical performance with choreography, staging, music, piano accompaniment, and acknowledgment of the audience.  Brilliant.