There is a theme park in Idaho called Silverwood, just across the border from Washington state. It had an unlikely start as a vintage airplane museum. Although is seems like a long way from the usual entertainment centers, it is a huge blast of fun.
It has a lot of rides, but the roller coasters and water park make it worth while. I think the Avalanche Mountain family raft water slide is the best ride in the park because of the combination of sheer fun and doing it as a group. At each turn, you slide way up the embankment, get soaked, scream and laugh yourself silly. The two wooden roller coasters are excellent. And late in the day the wait may be only one or two rides.
Melanie really enjoys the roller coasters! She rode the one at the Vancouver PNE as well as the Silverwood one. Notice that Melanie's expression is the same in both pictures - she is having a screaming fun time!
We drove out to near Spokane, camped at Little Diamond, spent the next day at Silverwood and returned the following day after camping again.
The weather was very hot. If you got wet at the water park, you would be nearly dry before getting on the next ride. It was a great trip.