It's probably just some fungus. Driftwood in tanks typically gets a bit of fungus on it shortly after it's been put in. Usually it seems to just go away on it's own, and some critters will eat it.
I'm guessing the power outage encouraged it, as well as maybe causing some of the water to go stagnant (my guess as to the odor).
running a filter with carbon for a bit is probably a good idea, and might help with the odor.
I imagine running it for a couple days to clear up the stagnation, and then maybe start the fishless cycling would probably be a good start.
The driftwood fungus seems to happen to most people, and I've never heard of any harm to plants or fish linked to it. Also, in my experience and from what I've heard from others, it usually clears up on it's own in a bit.