Heating or A/C confusion

As you can expect, I've been chatting with various people about my coming trip next weekend to Switzerland. Now I'm getting conflicting advice about how to best keep the engine from overheating. For those who don't know, I suspect I've got bad head gaskets, and am taking the car down to my original dealer (an SVX enthusiast) to find out what's wrong, get an estimate, and hopefully get it fixed.

Some say I should roll (push button? ) down the windows and put the heat on full.

Others say that if I switch on the air conditioning, then the second fan will come on and obviously two fans are better than one.

Sorry if I'm being extremely basic with this question but I frankly never really paid much attention to my climate control before. It worked, (still does) and that was good enough for me.

"I am extremely proficient at fixing my car: when something breaks, I get someone proficient to fix it!"
(quote attributed to ME)