Neither have an airside terrace, nor is there much but concrete and cars outside.

If they can enter Canada they can pass immigration and head to the exit before re-clearing security and US pre-clearance. Nexus will make it faster, but priority security from a business class boarding pass will avoid most of the security lines. A couple hour layover would be plenty if (this can be a big if with AC) things are on-time. I would recommend checking the security wait times on the airport websites before making the decision to go landside.