Pot you have to decide. Moth balls would discourage the furry creatures. If they get moth crystals on their feet they may be poisoned and die a horrible death. I'd go with the moth balls.
Though I've always had a cat and/or a dog who goes for anything smaller than a grown cat. 65 pounds of rat terrier. We don't put her in the attic.
We did have a furious squirrel attacking the front windows, the side windows, the front door, the front wall, then jumping up and down all over the roof. The cat and dog monitored this from inside ( I thought it might be rabid) until the squirrel calmed down and left.
Plot - remember don't seal up the basement until after the squirrel leaves. I still picture that one making his own squirrel door.
Stlight