Our family goes to 1,000 Acres Dog Park in the Sandy River delta at least once a month, especially during the warmer months. It's a spectacular space for both families and dogs, allowing for a broad range of activities and experiences, depending on your preference and the time of year. My family of four plays in the river during the summer, we bike there in all seasons, and take the dogs for runs in all seasons as well. A few things to know:

1. Parking is VERY scarce. People used to be able to park along Crown Point Highway right before the parking lot entrance, but guardrails have since been installed, forcing people into the lot, or up the highway to the parking lots at I-84 and at Lewis & Clark. There's now a $5 day use fee that you can pay right from your smartphone. There are also spaces in the center that are labeled as "RV/Trailer Only," but of late I have not seen anyone getting ticketed for parking passenger cars there. The demand is so high, I can't imagine Friends of the Sandy River Delta giving up on the revenue. Just watch out that you don't get parked in!
2. It being open and somewhat wild, with access from walking and biking paths, there is the potential for interaction with sketchy folks. I have heard anecdotes about run-ins with people who are less than friendly, but I have never had any bad interactions with anyone. The best practice is probably to stay on the highly-traveled paths and not wander off through the woods at the margins of the park.
3. It being an off-leash dog area, you'll encounter dogs. Some of them will get up in your business and beg for snacks, others will be wet and dirty and stand on your picnic blanket. Plenty will shake that wet dirt all over you. If dog interactions aren't your idea of fun, maybe consider hiking somewhere else!