I strongly agree with Kristan. 3-4 weeks in any of those provinces is better than an entire season in 3 of the 4 American flyways. One time is not enough, the more times the better. Your year will center around that time. After your first trip your mind will be there well before you are.
Drive, don't fly for the best experience. Expect fuel to be your major expense and your vehicle will take a beating. So will you, your dogs and all your equipment, but man o man is it worth it.
If it was close by, easy to get to and hunt without problems, it would not be the world class experience it is. Returning home to the rat race will take a toll on you, if you live to waterfowl hunt.
The Oak Hammock area is a sweet spot. You should have a very good time and see lots of birds, and shoot more shells than you are accustomed to. You won't be taking unfired rounds out of your gun again and again, like we do here on many days.
We took our shotguns in hard cases, broken down, or with the bolts out. All paper work in order, that includes your dogs.
If you cross at Pembina it will either be easy, or a very long and thorough check going in or out. We always stopped at the duty free to get what we needed. (If you like Rye, Seagrams 83 is some of the best you will taste and not sold in the USA.)
It's a good idea to roll all your windows down, so it's easy to see inside your vehicle prior to stopping. Making it as easy as possible for the officers to do their job is just common sense.
Take plenty of shells and extra guns. Declare all your ammo and pay the duty on it, as good ammo is hard to find. If you take dogs bring as many medical supplies for them as possible. Expect huge porcupines where you least expect them. Your dogs will find them, and badgers as well...
Once you go there and have a good experience. It Will Stay with you the rest of your life, and the birds you eat will become part of you. The memories burned like gun powder from paper shells.