Re: Robin or no Robin?
This might sound crazy, but I wouldn't mind Robin showing up right at the very beginning. Fighting alongside Batman, in full costume, no prior explanation (maybe some flashbacks or dialogue references later on, but not a whole movie's worth). I mean, even non-comics fans pretty much know who Robin is and where he came from, and it would be a great hook of an opening to see Batman and Robin infiltrating a bank robbery or a hostage situation, just doing there thing. Now, later in the film you could explain Batman's mission and how he has various operatives working for him, but I think Robin is one of those characters that, if taken seriously and not just made a whiny teenager, audiences could easily accept without a whole movie devoted to him.
In more practical considerations, I'm in favor of the costume Rorschach2012 suggested, and I always seem to imagine Logan Lerman (the kid from Percy Jackson and Meet Bill) playing him.