As our Christmas present this year from my Sister and her husband they took our family to Great Wolf Lodge water park in Olympia, Washington. We told the kids only that they were going on a surprise somewhere. We left the baby with friends who were kind enough to keep him overnight and we brought along our 7 year old neighbor boy.
As soon as we pulled into the parking lot and they could read the sign the kids went nuts! They were so excited, because they have been begging to go there since it opened 2 or 3 years ago. The place is definitely geared towards kids (and taking money from your wallets). My husband and I both agreed that we wouldn't want to go back again and that for your money you get more bang for your buck at Silverwood in Idaho as far as waterparks go, but we were glad that we got to experience it.
Everything there is expensive with a capital "E". Very little is complimentary and the extras when you have 7 kids, well, they just aren't worth it. If you have more than 3 kids I don't know that I would suggest going there.