The way I look at "my" characters, if you like, is that they don't really belong to me - I'm just someone who's lucky enough to be allowed to tell their story. Anyone else to whom they start talking - why, they're another storyteller, with just as much right to write about them as I have.
I honestly can't feel the same way as authors who get twitchy at the idea that someone's using "their" characters. To me, it's a great tribute if that happens - I've told a story that's good enough, that's portrayed the characters well enough, to inspire someone else. What could possibly be better?
The only thing I'd say as a caution is: listen to the characters. If they say "It happened this way," then you have to write that for them it did happen in that way. Even if someone else flatly contradicts them a minute later. Rob is constantly irked, for example, by the "Robin Hood mythos" because, as he'll tell you at great length, it didn't happen that way.
I suppose what I'm saying, really, is that the stories belong to the characters, not to the writers, and it's to the characters to whom any respect or delicacy is due.
If they want you to write for them, then I'd say you should go for it. Even if you don't show anyone, it'll let them know that they're appreciated.