There seems to be a bit of a double standard here:
1. Star Wars (The Original Trilogy) is not so important or great as to cause you to do much to not ruin it.
2. Star Wars (To include The Prequel Trilogy and the Clone Wars TV Show) is too important to not show your kids. You should buy them their own PT boxset for their birthdays.
If it's not important, why is it important that I haven't shown the PT to my kids?