I think 80ma is too much current to be delivered directly by the AVR. I think the specs have a limit for sourcing/sinking current of around 40ma. You should use a couple of small transisters (or opto couplers) to actually drive the fans. In addition, you should considered the potential EMF voltage feedback from the fans (inductive loads) when the current is shut off. The opto couplers would be the best best.
This is so much a safety issue as it is a longevity issue. Attempting to provide to much current with the AVR can cause the chip to fail and the EMF from inductive loads such as fan motors can cause hard to diagnose failures.