I have had some of the best luck finding summer mushrooms in the Olympics and along the Straight of Juan de Fuca on Vancouver Island. If I could choose anywhere right now, I would pick coastal Oregon, Washington, and British Columbia. Still, I managed to find a Bears Head (Hericium) last weekend in the western Cascades near Mount Rainier.
Here is a link to all of my July/Aug finds over the past 5 years
(iNat)
Here are some of the species you are most likely to encouter in July/Aug
(iNat)
Follow the Rain
You can improve your chances of finding mushrooms during the dry months by searching out places that have been getting rain. Here is a link to NOAAs precipitation map. You can use the timeframe options at the bottom to change to 7 or 14 day accumulation
https://water.weather.gov/precip/
Find a Hike
The Washington Trails Association (wta.org) is an excellent resource for finding trails and trip reports. Find hikes good for kids or dogs, check trail conditions, check for mosquitos, and see what berries might be ripe.