Greystokes is right next to Big White and is the best place to ride in Kelowna. A lot of locals don't like it due to the lack of "Big Mountains" but it gets some great snow, is a huge riding area and has spots of decent climbing.
I typically like riding off the 201 Forestry Road. It's about 3 or so KM up Big White Road and is the road that banks left and goes up a hill. I drive about 20KM up it and unload. I avoid most of the trails this way and can get some tree riding in.
The main parking lot at Greystokes in off Three Forks road, but has a 15km or so trail to the main cabin, and another 10 or so to the "Hiltin cabin" which is closer to the good playing areas. The club doesn't groom often enough to make those longer treks enjoyable for me.
Being that it is such a large area, it is easy to get lost up there, so I advise riding with someone. Depending when you go, PM me and I might be able to give a tour. I usually follow other people, but know my way around decently.