WOW, holy crap I had no idea I'd get all of this feedback on here...
I need to explain a lot more, I apologize. They do not want and will not stand for a "pro" experience here, that's why I said that isn't an option, even if I wanted to spring for it for them. And most importantly, they're not asking me to replicate it.
These are two very non-traditional/alternative 30 year olds that have been to a SHITTON of weddings and they despise the idea of a traditional pro photographer (and a boatload of the other traditional wedding activities). They've hated watching photographers trying to document every little thing and other than a shot of the two of them and them with the parents, there will not be the litany of group shots or any other posed shots. They've made that very clear from the beginning of the discussion.
They're all about just enjoying the day (including me), not documenting it or doing things that they don't want to bother with just for the sake of "tradition".
SO, with all that being said, this will not require 500 shots (they'd probably be upset if I came anywhere close to that) because 1. they don't want all that and 2. they want me to still enjoy the wedding myself.
I fully expect that there will be hand-out cameras for folks at the reception and those are the kinds of photos they'll really love (you'd just have to know them to understand). We did that at our wedding and have seen the shots from many others, it's really cool and I recommend it.
I want to be able to do a good job on the handful of posed shots, and it sounds like a separate flash and the flip mount would be a good idea.
I have a nice tripod I got myself a while back, so that's set and I have a spare battery and card for the camera (probably just get one new one to give them afterward with a disc of the shots as well).
I've never shot RAW and I've never post-processed anything. I've always tried to get it on the camera based on learning on film. For this, it sounds like a better idea to do RAW and either find someone or let them find someone to do the post on the shots.
Oh, and I was wrong on the lens I have, it's an AF-S Nikkor 18-135 1:3.5-5.6. I've really liked it in the four months or so that I've had it. From what I've been told, the yard/area for the ceremony isn't large, so I don't think I'll need anymore zoom than that. Maybe I can get them to give me a photo and some dimensions...
Great suggestions folks, but let's drop the idea of backing out of doing it
I understand where you're coming from but this is far from the types of situations you're thinking about, you'll have to trust me on that one.