Welcome. Can't speak for the $ value of duty for extra beer or alcohol, if it is only one unit per person and your upfront declaring it, they may just let it through, as said before lots of different choices up here.
Fruits, veggies, meats, may be questioned or you could be asked to put them in the garbage. Sounds like you have a good plan and that will make the crossing much easier.
The Niagara River Parkway, very pretty, towards Niagara-On-The-Lake/Lake Ontario has lots of fruit and vegetable stands, excellent quality.
Have a great trip,
Beverley and Ken