Having never had on-bike storage before, or a bike designed to cover big distances, I'm thinking about what I could leave in the bottom of the panniers to keep us on the road.
Here's the short list so far:
A bike specific multi-tool, this BikeMaster metric device covers a lot of bases in terms of general usefulness.
$16.18 from canadasmotorcycle.ca
Puncture Repair Kit. Many moons ago I used to do this at Canadian Tire, so plugging a tire is nothing new, and if I've got the bits I need on the road I'll be able to get us going again in short order.
$~20 from Canadian Tire
Yukon Steel Multitool. I use a generic one at work all the time. They work well and I don't need a fancy brand to somehow validate my handiness.
$30 from Canadian Tire
I'm also going to grab a lightweight nylon tarp. You can get tough, camping ready ones that only weigh about 500 grams and fold up into the size of an envelope. Along with a little roll of duct tape, small hand pump, some nylon string and a mini wd40 can, I'd have a very light and small collection of handy bits and pieces that would keep us moving if we ran into a problem.