A few years back we stayed at a b&b in Summerland (maybe 20 minute drive away?), and we could have used the kitchen there if we wanted, so it's worth looking around. Also look at Craigslist (or even VRBO??), you may find a private condo to rent.

Note that on both sides of the lake there are rather steep hills, so in our case getting back after a ride meant finishing on a notable effort. You could always park a car at a lower altitude though (less practical). All this to say that if you rent outside of Penticton itself, make sure you look at altitude data to avoid getting a surprise.

It was a nice ride into town to watch the start of the race. I am not certain about parking anymore but I'm pretty sure you could have someone drop off your things, too.