That line about "I just want it to last" hits home. Everyone gets stuck on the smooth finish. For freeze-thaw, you need a mix that can breathe a little and handle getting wet. I'd skip the fancy stuff and go with a standard 5-sack mix, but make sure they use a good air-entraining admixture. It puts tiny bubbles in the concrete so ice has room to expand without cracking. Looks aren't as important as getting that right.

That trick with the spray bottle butler.ivan mentioned is smart. It reminds me of a crew I saw once that had rigged up a simple shade cloth on poles over the section of wall they were working. It was just some old canvas tarps, but it cut the direct sun and dropped the surface temp of those bricks by what felt like twenty degrees. They weren't fighting the mortar at all. Sometimes the old low tech fix is the right one.