"Supermoon" means the moon is full and at its closest approach (perigee) to the Earth, meaning it will look larger than usual (and 14% larger than at apogee). There have only been 5 of these since 1900; the last was in 1982, and the next won't happen until 2033.
It will be especially convenient on the U.S. west coast, because the moon rises early in the evening, so kids will be able to see it without staying up late. This site has details for many of the major cities that will be able to view at least part of the eclipse -- western Europe will be able to see the ending of the eclipse Monday morning, and New York City can view the maximum at 10:47 pm Sunday evening.
The Oregonian has details for this part of the world:
For viewing in Portland and northern Oregon, the eclipse begins at 5:11 p.m., Sunday, Sept., 27, 2015. That's before it gets dark and before the moon rises, but it only gets better.
The maximum eclipse is at 7:47 p.m. next Sunday evening and continues until 10:22 p.m., for a duration of five hours and 11 minutes. For 72 of those minutes, the only light hitting the full moon will be a reddish glow from sunrises and sunsets around the globe. The full moon takes place at 7:50 p.m. PDT next Sunday.
The moonrise that evening is at 6:58 p.m., at 88 degrees (or almost due east). The sunset is at 6:59 p.m., so the sky should be getting dark as the moon goes into its full eclipse at 7:11 p.m. next Sunday. The moon will be just 8 degrees above the eastern horizon at the instant of the greatest eclipse, making the event more spectacular than during an eclipse occurs with the moon high overhead.