I'd be going for the lower end of cellar temperature for the guezes, so fridge-then-left-out-for-a-bit sounds about right. The krieks you can serve chilled.
Mort Subite Geuze is quite disappointing, but I've a soft spot for the Timmermans-made Bécasse stuff. A La Bécasse is a contender for My Favourite Pub In The Whole Wide World.