Looks like a great ride! However I would like to make a suggestion for the beginning of your ride, an alternative to the Osoyoos/Keremeos/Penticton route. And that is the Osoyoos/Oliver/Okanagan Falls/Penticton route.
Starting from Osoyoos, head north for a few clicks on Hwy 97. Turn right on road 22, which turns into Black Sage Road once over the bridge, and follow to Oliver. Very quiet road rolling past several vineyards with nice views to the west. When you reach the stop sign in Oliver carry on across the intersection and the road now becomes Tuc-El-Nuit Road. Follow this road past Tuc-El-Nuit Lake and merge onto Hwy 97 north of Oliver. Follow the highway past Vaseux Lake and into Okanagan Falls, making a pit stop at Tickleberry's Ice Cream Emporium if one is so inclined. Carry on to 7th Ave, one block past the 97 turnoff and turn right, then left on East Side Road. This windy road follows the shoreline of Skaha Lake most of the way to Penticton.
So thats it, some nice, rolling country roads, vineyards, an impressive rock bluff and other cool geologic formations, 3 lakes and not a lot of traffic in the spring. Mostly travelling in the 50-80 kmh range. Oh yeah, and Tickleberry's. One of the nicest road bike rides around.
On the other route right off the bat you have Richter Pass, a big high/lowlight of the Penticton Ironman Triathlon. Many a grown man and woman have shed big tears on the side of that road. But don't despair!! There are many more giant hills to follow. There are some nice views on that route as well but you may not get to see or enjoy them while you are battling the unceasing wind and the cars and trucks whipping by at 100-140 kmh.
Whichever route you choose, you guys have a great time. And if you see someone on a white Specialized Roubaix, looking like he may have stopped for a few too many tastings, give him a wave!!

Mike