Annie's playground ( http://www.anniesplayground.org/playground.html ) is a wonderful playground for kids that love to climb. It is a newer playground, close to Nathan Hale High School, the Meadowbrook Community Center and Meadowbrook Pond. The parking lot is located off 30th.
This playground has the most climbing structures so far out of all the playgrounds I have visited. There are three main structures, varied by level of ability. A wee toddler structure, a middle sized structure with a mini climbing wall and a big toddler structure for the older kids.
Along with the cool lounge chair seat swings, tile art, teeter totter, this is one of the best, not so crowded playgrounds in town.
If you also have a little naturalist, we usually walk across 35th to Meadowbrook Pond to visit the beavers.
This is a link to Seattle Park and Rec's page ( http://www.seattle.gov/parks/parkspaces/meadowbrookplayfield.htm ).