I'm confused! <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />
I have seen all of the following:
Elf: Elves - Elfs; elven - elfen -elfish
Dwarf: Dwarves - Dwarfs; dwarven - (not dwarfen or dwarfish, though)
What is considered correct spelling <img src="/ubbthreads/images/graemlins/question.gif" alt="" />
Elf with a plural of Elves. (elfs and elfen are generally considered incorrect (i.e. non tolkien) <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> of course it's your world...)
With Dwarf it's a little different, Dwarves or Dwarfs are sometimes used interchangeably. I favor keeping with the Elvish tradition, and using Dwarves, but most english readers won't bat an eye are Dwarfs.
(usually dwarfs is used to refer to a collection of individuals, where dwarves is used to indicate the race/species. Ex. A group of dwarven warriors (indicates race of all warriors), versus, The group had some dwarfs (indicates individuals were OF / FROM a race, but perhaps not the entire group))- although again, personally, I always like use dwarves for all such cases.
Yes dwarfen or dwarfish would be seen as "incorrect".