You can enjoy and appreciate this video; for your children this will be meaningless, because the science behind the experiment will be irrelevant with digital television.
Because the picture is formed by steering the charges with the electromagnetic coils, any additional external field in the nearby vicinity is going to alter the field between the coils. This is going to affect the electron deflection, resulting in a distorted, fun-house-esque picture on the screen. It's also important to note that a strong enough magnet can permanently magnetize the copper coils resulting in a permanently distorted picture. Bear that in mind if you ever try this at home.