If you like garlic and getting out into the countryside, the garlic festival offers a good ninety minutes of entertainment for all ages.
August 8th - 10th, 2014
Jessie Mays Community Park, 30975 Hillcrest Street, North Plains, OR [Google map].
Comprehensive listings of family friendly Portland based events
Jody manages an awesome collection of things to do!
A blog devoted to getting outside and exploring.