I'll definitely pick up that app. Is it pretty easy to navigate the basics of Pemberton and Squamish with the maps? Ideally we'd like to piece together a nice long day, say 5 to 6 hours, each day.
As far as the mountain goes I was planning on bringing my armor and DH tires to put on my AM rig, which will be a Knolly Chilcotin. I plan to do a bunch of park riding locally with this setup so we'll see how that goes. I probably have the most park experience out of everyone so I'll definitely put the rental idea out there.
The apps are awesome (you actually need one app per location I think). They map your current location against the trail map which also has topography so you can gauge whether you're at the correct junction. They are very easy to use.
The Chilcotin with big tires is a very capable bike but if you're only doing a couple of days in the bike park I think you'd have more fun on a rented big bike. It'll ride better and save your Knolly that horrifying wear and tear.
There's nothing better than an Orangina after cheating death with Digger.