Some of the KH characters have alternate name spellings, yes (there is a difference of opinion on how to spell the name of Lexaeus' other, for example- and other people just go by personal preference) but not all of them.
Anyone who's original Disney- really, seriously- there's a right way, and a wrong way.
Example;
Jiminy Cricket is spelled with one m. If you don't trust me you should at least trust
the official Disney website.
So. Please double-check if you're unsure? Hell, even when you are sure, because typos do happen!
You may be looking at this post and thinking 'what's the big deal'?
It's the same big deal for misspelling a word. When your fic is peppered with misspelled words, you look inept, and fewer people will want to read it. You should have more respect for your own writing. Just like you should spell-check everything- you should double check the names.