As a longtime fan of Tolkien's work and Kingdom Hearts, I really, really love it when someone attempts to cross the two together. However, in the case of your works, I'm afraid I don't like them. At all.
First point to writer number one: If you are going to be following movie!canon, why have Elladan and Elrohir, characters who were not in the movie yet played a part in the books, make an appearance? More importantly, why in Elbereth's name would you include them and not spell Elladan's name properly?! On that note, it's "Merry," not "Mary."
Second point to writer number one: Why have the Radiant Garden gang be in this at all? Why not just Sora, Riku, and Kairi?
Third point to writer number one: Why have Merlin bring them to Middle-Earth? Furthermore, why imply that Merlin is a native of Arda? Are you trying to say that he's one of the Istari? BULLCRAP!
As to you, second writer, my complaints can be summed up as follows: Kairi is not a bitch, nor is she a "brunet." Sora would not angst about trying to fit in back home. Also, how can Arda be in the same universe as Kingdom Hearts and yet not have it's own door? Although I must admit that the scene where Sam fights off Heartless with his frying pan is rather cute.
So to anyone who wants to crossover Tolkien and Kingdom Hearts, I have this to say: Do. Your. Effing. RESEARCH!