There weren't many campsites to be found on Mabel Lake so I decided instead to do a six day trip on the Shuswap Lake from Sicamous to the top of Anstey Arm.
It was an awesome trip. Shared the lake with a few houseboats and power boats but still ended up having four out of five nights where I was the only one occupying the entire campsite(s). The lesser travelled Anstey Arm is a very cool place to paddle with incredible scenery, from the top there are no buildings in sight as far as you can see, and very few houseboats as it's too shallow for them.
Campsites at Anstey View, Anstey Beach, and Marble Point are nice -- each has a covered picnic table and an awesome view. If you're comfortable with a few boat wakes, the Shuswap can be a pretty cool place to paddle.