Jenkins Estate would be a much better choice. It's very close to Cooper Mountain. It's just a bit West off of Grabhorn Rd. Playground, rent a shelter, tons of green space and BBQ's. Contact Tualatin Hills Park and Rec for rental info and availability.
See that this is actually a nature reserve, BBQs are most likely prohibited, including near the play structure. There are tables and benches throughout the park, but I don't believe any of it was intended for private parties. Please contact the Park District for a more clear and official answer. They will be who you'd book the space through anyway if they allow private functions.
Yeah some tables exist to sit but restrooms closed now.
You could probably have it outside at the picnic tables but they would be first come first serve. There is no bbq there
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