Since I asked the question, "What would you like to see..." I should have known what to beware of. I could handle almost all of the requested items in my backyard but my hot tub only holds 23 people and I don't put water in my waterslide until after Memorial Day.
Perhaps something more realistic could be considered. I stayed in a National Park Service campground (Spring Canyon, just about a mile above the Grand Coulee Dam) last October. It has a group area that can be reserved and I am presently attempting to secure it. It is presently available for the weekend of May 14-16. There is a lake (Roosevelt) a hundred yards away, clean bathrooms with showers, no electricity, and a cost of about $10 per night per site. Trees, grass, sandy beach, fishing, boat marina, one of the world's largest concrete dams very nearby, great geology all around. More information available at www.nps.gov/laro/planyourvisit/campgrounds.htm
I could figure out a "slip and slide" for kids but it might be a bit cool that early in the year.
Your realistic thoughts? Does this site seem like somewhere you might want to camp?
Dave