Like others have said, take a day trip down the Seward Hwy... beautiful drive especially if the clouds stay high or get a lucky sunny day. Stop in Gridwood/Alyeska, continue on to the Portege Glacier visitors center... and for a real unique treat, drive through the north america's longest highway tunnel through a mountain to Whittier located on Prince William Sound. Your son will get a kick out of driving through that tunnel, driving along railroad tracks in the center of the earth! This time of year it will be "dead" in Whittier, so you'll have the whole place to yourself, but if you like scenic drives and nature, along with some history, its a good option.

When I say day trip, it's not as long as it sounds.... it only takes about an hour to get to Portage Glacier if the roads are good... it's just that there less than 8 hours of daylight right now.

Earthquake Park in Anchorage is also interesting and close.... dress warm!