While melting and pouring wax is best left to adults, the creative parts of this candle-making project (choosing the perfect crayon to color the wax and decorating the glass holder with beads) are meant for kids.
Set up a double boiler to melt the paraffin. Fill the bottom of the saucepan with 4 to 5 inches of water and drop in the canning jar lid rim. Then pack chunks of paraffin into the coffee can, setting it on the jar rim so that it doesn't directly touch the bottom of the pot.
Melt the wax over medium-high heat, carefully adding more chunks until the can is about two-thirds filled. To color the melted wax, break half of a peeled crayon into pieces. Add them to the wax and slowly mix with a paint stirrer, then turn off the heat and let the paraffin cool for about 10 minutes (this will help minimize shrinkage when the wax hardens).
Using a sharp knife, cut the candlesticks 1/2 inch shorter than the jar heights (adults only). Now, heat the jars by running warm water on the outsides but not the insides (this will help prevent cracking when you pour in the hot wax).
With metal tongs, dip the bottom of each candlestick into the melted wax and stick it to the inner jar bottom. When the candlestick ends have hardened enough to hold, carefully pour enough wax into the jars to cover the candlestick tops but not the wicks.
Once the candles cool completely, your kids can glue beads to the outside of the jar, arranging them in a border around the rim, perhaps, or creating a multicolor pattern all the way around.