Using a large bulletin board, place pins strategically to outline a cross
. Wind a piece of string around the pins to create the form of the cross. Cut small pieces of black or brown construction paper. Explain to the children that Jesus died for our sins - things we do but know we shouldn't do. Talk about the things we do that are wrong - sinful. (e.g. lies, taking something that doesn't belong to us, hitting someone, talking bad about someone, etc) Let everyone write their sins on the small dark pieces of construction paper (one sin per piece) and pin it within the outline of the cross. Encourage everyone to add more of these pieces as they reflect on their sin, and when new sins are remembered.
Take off the sin papers, leaving the pins in place. These pins hold the memory of our sins which Jesus died for, and will now be used to hold decorations.
Create flowers out of construction paper and pin them on the cross with the same pins. An artificial vine with flowers could also be wound around the pins to create the triumphant cross.
The sin papers are then burned by the Easter fire: a white candle symbolizing the new beginning we have in Christ.
Variation
Instead of construction paper, use pieces of "flash paper" available from a local magician's shop. When touched to a flame "flash" paper vaporizes in a flash of fire and leaves nothing behind. Warning: Have a teacher touch the papers to a flame and quickly let go to avoid getting burnt.