Thing with Carr's Landing is that it's a great location, but a bit of a pain to get to off Hwy 97. Whether your approach is from the north or south, it's a narrow road once you leave the Hwy, & it's about the same distance from the north or south once you exit the Hwy. Hope that makes sense. In any case there aren't any other RV sites along that road that I know of so you're going to be lucky to get anything closer than the 20 to 30 minute range from there.
I did a little checking & found this:
http://www.woodlake-terrace.com/
It's on Wood Lake between Oyama to the north & Winfield to the south. Closest I could find and probably not the best location since it's just off Hwy 97, so traffic at night could be an issue. If there was a road over the ridge between there & Okanagan Lake, you'd be at Carr's Landing in 5 minutes, but unfortunately, there isn't. You have to go south to Winfield before you're able to access the road to Carr's Landing. On the plus side, there are some top notch wineries along the way.
If I remember correctly the brother of a fellow soccer player may also have some camping/RV sites on the other side of Wood Lake. If I see him next Thursday, I'll confirm if that's an option.
If you have a boat, there are a couple of places on the opposite side of Okanagan Lake to Carr's Landing on West Side Road. Boat ride would be fairly quick across but you can forget about going anywhere by road from there in a hurry. Westside Road runs from Spallumcheen north of Vernon all the way to the south end of Kelowna, with no opportunity to exit, unless you drive into the lake or up the mountain on a Forest Service Road.
Best of luck with your hunt for a spot. The Okanagan is a popular spot in the summer. I'm always rather glad when fall rolls around & all the excitement dies down again.
EDIT: There's also Kekuli Bay Provincial Park a bit farther north on Kalamalka Lake. Worth checking into. Again, close to the Hwy, but a pretty spot & Kal Lake is much nicer than Okanagan Lake IMO.