Having benefitted so much from the advice from these forums, I hope that I can contribute in some small way. :-)
In addition to its Cottage Tents, Whistlers Campground now has an Otentik tent available to book.
There isn't much info on what an Otentik Tent is, but I emailed the park and they confirmed that it is the same one in Riding Mountain National Park. LInk for description: pc.gc.ca/pn-np/…activ2_ix.aspx
Sorry, I don't know how to hyperlink here!
It looks bigger than a cottage tent and I think the small covered deck area will be useful in case of rain.... at least you can be outside the tent but still dry.
Hope that this info is helpful!