There is a tremendous amount of boat activity on that water. I am on there regularly and have been for over a decade. Bass fish all the docks you wish however my suggestion is to plan on very early morning or very late afternoon when the boat traffic is at the least.
There will not be lack of activity on the water or lack of people watching, that part of the river is fun, busy, and great!
I am assuming your above the damn and boating out to cda lake and along the Spokane river is enjoyable.
Depending on the dates I would be willing to lend you my runabout (2000 Bayliner 2050 with the V8) if you guys could use a boat. I normally would not offer this up but in light of all that your family has been through....
It is fully insured with liability over a million and I would simply drop it off meeting you at the boat launch an go if your interested. You may borrow it for the time of your stay if there is a dock.