Get a Costco membership.. either rent in Plattsburgh or Albany. It will be cheaper and booking through Costco you won't pay 2nd driver fee. Renting up here is going to be pricey with additional fee to take car to usa. Although I think through Costco it's waved at Alamo/Enterprise, Avis/Budget.
Pretty much everything is unlimited KMs now unless it's super premium. I don't even bother with online discount codes anymore. I use Costco's booking site