Find a friend with a laser disc player or a Karaoke machine and rent some Karaoke Discs (screen the songs beforehand- a lot of the videos are pretty raunchy). If you don't have a professional Karaoke machine, you can hook up a laser disc player to a sound system and a 19″ TV that the person that's singing can see. Have the video input split so it is projected on a large screen behind the person.
If you have the ability, send the music through a set of earphones (so the person singing can't hear themselves too well).
If you use a video mixer and a camera, you can shoot the person singing and place them on the screen in a wipe mode or mixed in.
Have the music play through the earphones only during a song or two so you only hear their voice out loud- always good for a laugh.
Jonathan McKee is the author of over twenty books including the brand new The Bullying Breakthrough; The Teen’s Guide to Social Media & Mobile Devices; If I Had a Parenting Do Over; and the Amazon Best Seller - The Guy's Guide to God, Girls and the Phone in Your Pocket. He speaks to parents and leaders worldwide, all while providing free resources for youth workers on TheSource4YM.com. Jonathan, his wife Lori, and their three kids live in California.