We did a little trip down the Washington and Oregon coasts last year around this time. The coastal part went pretty well (except for some extreme Simon meltdowns from his extreme hunger). Did the Oregon Coast Aquarium and what not. Then we went to Portland, and did almost nothing because it was rainy and crappy.
This year, we thought we'd spend a few days in downtown Portland again, but looking at the weather, decided to bail on that plan. Looks like they're having the same craptastic cold weather we are. So we came up with a plan-B.
We'll wing it most of the weekend, and if it's nice enough, go to the Woodland Park zoo or something. When everyone else is ending their weekend, we'll do an overnight at Great Wolf and give that a try, since it depends not on weather. There's a Microsoft rate that's about $70 off, which is crazy awesome (must remember to bring employee badge).
There aren't many places to do driving trips to in this part of the country. Granted, there are many places to explore right here in Western Washington, but beyond that you have Portland to the south and Vancouver to the north (need a passport), each about three hours. Northern Idaho (Silverwood) is about five hours. Lots of flying destinations under three hours though, including Las Vegas, LA (blah) and San Francisco.