One word..... expensive.
You can check out the cabins at Cultus lake, as they're not far from the water and hills for quadding. They go for about $700+ a week though.
Other than that, the Okanagan is an option, although quadding in this heat may not be recommended in the fire prone areas. Also, up around Merritt there are some options.
Check out Craigslist for rental properties.