The major campground for the area is Steamboat Rock State Park which is a reservation-only state park (do a search for latest fees and instructions). The park has spacious camp sites with full hookups, lawns, bathrooms/showers, swimming areas and lots of sand beaches. Launching is convenient at the north end of the camping area adjacent to the boat ramp on sand beaches. There is a charge to launch and park (unless you have a disabled permit).
From the park launch ramp I like to paddle north into the maze of islets. The area is not large but it's still pretty easy to get mixed up in directions although you can't really get too far off.
The water in summer is warm enough for swimming and you can easily carry camping gear and find places to pitch a tent on the islands. Stores and restaurants are convenient in Grand Coulee about 14 miles north and there is a free laser show on Grand Coulee Dam in the summer every night.
This area of Washington State is dry and arid and days are typically warm and sunny while nights cool down. Watch out for thunderstorms. There can be mosquitoes but no biting flies. Outside of the park you could find rattlesnakes. Although I've never seen one my daughter's two huskies found one at a rough campsite on the north end of Steamboat Island.
The waters of the Eagle Pass area are well protected but there can still be significant afternoon winds generally from the west or northwest. West of Steamboat Rock the water is more exposed to the north and south and waves up to 2' could occur. Also, due to the popularity of the lake for fishing there can be a lot of power boat traffic; especially on summer weekends. This traffic can be significant on major holiday weekends.
Coulee City has a nice municipal park on the water next to US highway 2. There are several privately operated parks near Grand Coulee. Restaurants, stores, fuel and pharmacies are located in Grand Coulee plus a casino operated by a local native American tribe.