Christina lake is way to bizzy for my liking.....But if your into Kootenay Lake and full hook ups i'd recomend Woodberry resort, the sites are kinda small but they have a pool, small playground and a large sandy beach, the fishing there is fantastic (I saw a 19pd rainbow get pulled in there a few months ago). If you stand at the mouth of Woodberry creek I here it's good place for fly fishing as well.
It's aprox 20 min south of Kaslo.

I was going suggest Christina as well a a nice place but thought am a little biased as grew up there.

Texas Pt is good, little rocky, beach on the south end is sandy but day use only.

Muck I think it was just the provincial park, we could reserve and always got a place close to the beach, and the site secluded. If I remember correctly, they always had fun stuff going on there as well, interactive things about wildlife etc.

http://www.env.gov.bc.ca/bcparks/exp...kpgs/moyie_lk/