Hi Craig,
First, all Parkers are nice guns, second, it would benefit you to join the PGCA even if it is just to sell your grandfather's Parker.
After you learn a little more about it you may change your mind. You've hit the right place as the members here are great guys and with some more pictures would be happy to help out. A close up of the stock, butt plate, bottom of receiver, your grandfather's repair and the top of muzzle would be good start.
I would certainly offer it for sale on this forum (you need to be a member first - very easy) as you will reach interested parties both in Canada and the USA. I am in Victoria.
There is a process to go through selling into the USA and it will add around $400 to $500 to the price when the dust settles for a US collector. Prophet River is an excellent place to start if you want to export - their on the web - can't recommend them enough.
Good news is your brass shot shells are worth anywhere from a low of $10 to a high of $25, or more, if sold separately although I am no expert in shells so please get another opinion.
They were made in Canada by Dominion at the turn of the century or before which is neat if your a Canadian collector. (I would be interested in a couple of them myself)
From your first pictures the gun will be interesting to someone and with a little more info you'll get a clear picture of value. In Canada you can also list with Canadian Gun Nutz which is not an auction site - funny name, good organization.
This site - PGCA - will tell you when your gun was built, just look up the serial number - (I would have done it for you but don't know how to save this message) - and also if a research letter is available which will add value to your gun. Again well worth it to join PGCA.
Careful though, once you start to learn about Parker's you may get hooked! Hope your grandfather's gun gets to a good home - maybe even yours.
Cheers John Gardner