When to Go
May to Oct (the park is partially open in winter also, but may be a difficult trip with young kids)
Things to Do
Trails, enjoy spectacular views, boat tours on Diablo Lake
Tips
1) The northern (Ross Lake) and southern (Lake Chelan) regions of the park are far apart and not connected by road, making it difficult to visit both areas in one day. You need to make separate plans to make two separate trips in order to visit both areas.
2) If your family is not used to spending long hours in the car, make it an overnight trip.