You can do a nice little tour of the interior from Kelowna. Big White is about a 45 minute drive from Kelowna (maybe less?) and is a great mountain when the sun shines. Check the weather - if it's calling for fog, steer clear as Big White Out isn't much fun under those conditions. Silver Star is about an hour and a half North (20 minutes up from Vernon), and is a decent mountain (I see you're from Ontario - scratch that - an excellent mountain! The headwalls are a treat - remember - it looks steep but out there, your skis actually have something to grab on to). Silver Star gets loads of sunshine too. Sun Peaks - is bigger and better than Silver Star and also lots of Sun.
Whitewater is a bit of a hike as I recall (maybe 4-5 hours from Kelowna?), and in my opinion, unless you're going off-piste, the mountain will seem small. BUT Nelson is about the cutest town I've ever been in - worth it just for that. I believe that's where the movie Roxanne was filmed.
Saving the best for last, Red Moutain is amazing. And Rossland is a great town. Go there.
I haven't skied Revelstoke but it's on the top of my list, and it's not that far away from Silver Star. The other must ski hill in BC for me is Kicking Horse, but I think it would make for too much driving if you're going to fly into Kelowna - which I would recommend.
The Alberta side of the mountains has great skiing, but there's a chance you'll hit really cold temps. My view on that is if I want cold I can ski Tremblant; when I go to BC, I want reasonable temperatures. Go interior.
Unfortunately looks like not a great year this year, but there's perspective there. I spent a season teaching at Silver Star, and I remember vividly one day during Ontario March Break: Ride up the lift with a local family and they talk the whole way about how cold and icy it was; next Ride up the lift is with a family skiing there from Ontario and they talk about how warm it is and how great the snow is.
Along those lines - at the visitor's centre in Nelson and the staff tells us to dress warm because it's going to be really cold tomorrow. I say "how cold?". She says "where are you from". I say "Ottawa". She says, "You'll be fine - It's going to be -7". Perspective!
Have fun. And if the skiing is bad, enjoy the wine!
Finally - here's a site with some info on all the BC resorts, along with base depth:http://www.hellobc.com/en-CA/SightsActivitiesEvents/WinterActivities/Skiing(Downhill)/BritishColumbia.htm