Well, the saying 'swearing like a sailor' in stories can be non-mandatory, you know.
Actually, if you think that you have to put it into the writing, than you may consider reading Tolkien's own stuff. If you read the LotR and Hobbit carefully, then you'll find that the word 'damn' is only used once in the entirety of the trilogy (and I'm pretty certain that it wasn't used in The Hobbit) and 'hell' is only used once in the Hobbit. The first by one of the two orcs in the chapter 'The Choices of Master Samwise' and the other by Bert or Tom, one of the trolls, I can't remember which, in the chapter 'Roast Mutton' (in The Hobbit).
Other words used as exclemations, strong or otherwise, was 'good heavens!' (by Frodo in Three is Company, I believe) and the hobbits often 'dratted that wizard'. I can't remember anything else in particular. Ah, yes. . . one of the trolls also said 'blinking', but I don't know how official that was.
Whatever help that is. . .come up with a few other ones, but make them innocent, how 'bout? *sweet smile*
-- Folwren