Keep the can on the table and the knife pointed into it to avoid getting poked. Children should have an adult do this for them. Larger aluminum cans are often open enough that you can fit in the candle and avoid cutting.
Another way to cut the can is to make a slice on the outside using an x-acto knife and then cut around with scissors, but beware of sharp edges.
Use a tea candle or LED light to avoid heating the can while in use. Cans with the tops cut off and decorated can also be used as pencil holders.
Be careful of sharp edges.
The hole punch dulls the edges, but use sandpaper or an emery board to file down any sharpness.
Chains, rings, and backs can be recycled from old jewelry you have around the house.