You can buy there what you want to bring back into Canada as well after your trip. ie. Buy 3 bottles of liquor for a couple, take 1 bottle down to Orlando and leave the other 2 bottles in your car trunk. When you come back to Buffalo, you already have your dutyfree exemptions for your return. Plus there are usually deals / specials on 3 or 4 bottle purchases.
If you have another question, let me know. I work at the Peace Bridge Duty Free and I'm a fellow Disney fan!