I'm by no means an expert, but I do believe that heating it up will A) change the flavor and aroma of what was pristine cider, and B) not kill as much bacteria as campden tabs will.
My first batch of cider is in the fermenter now. I added campden tabs, then pectic enzyme 12 hrs later. 12 hours after that, I pitched my White Labs English Cider yeast, which had been bubbling away in an apple juice starter. The next morning, I had a 3/4" thick krausen, and it's still bubbling away right now. So to answer your other question, I don't think that the campden tabs will hurt your yeast if you wait long enough, and I've never heard of it causing any off-flavors.
Use the campden tabs. Safer that way. My $0.02.
MOSS HOLLOW BREWING CO.
Aristocratic Ales, Lascivious Lagers
•Scottish 80/- •Sweet Stout •Roggenbier
.primary | bright:
98: Moss Hollow Soured '09 72: Oude Kriek 99: B-Weisse 102: Brett'd BDSA 104: Feat of Strength Helles Bock 105: Merkin Brown
.on tap | kegged:
XX: Moss Hollow Springs Sparkling Water 95: Gott Mit Uns German Pils 91b: Brown Willie's Oaked Abbey Ale 103: Merkin Stout
98: Yorkshire Special 100: Maple Porter 89: Cidre Saison 101: Steffiweizen '09 (#3)