The retiring of the American flag is to be done in a respectful manner. Just dumping it on the backyard fire pit is not the proper way to do this.
http://www.ushistory.org/betsy/more/flagburning.htm or
http://www.flagkeepers.org/Home.asp
I suggest the local VFW, American Legion, Fire Dept. or the scouts. They will all carry this out properly. If you wish to educate your kids, I'm sure one of these organizations will allow yow to attend the ceremony.