Q:

How do I shoot massive bonfire in order to produce an HDR image?

I am looking for advice on how to shoot a massive bonfire to produce an HDR image. My school has a massive bonfire every year for homecoming — it is 30+ ft. tall. I have been shooting and HDRing my photos for a year now and have gotten decent results during daytime shooting, but I have never really taken an HDR shot at night.
I have a tripod so I am not worried about getting an image; I am more concerned with the best way to get the series of images for an HDR'd image. Should I take one RAW and manipulate it into five JPEGs during post, or shoot five shots that night? Also, I would like to get as crisp an image as possible of the flames. Are crisp flames a pipe dream?
Just in case this helps: I will be shooting with a Sony a33, which is pretty good in low light, and either a 50mm/f1.8 or a 28mm/f2.8. All mounted on a tripod.
The fire is pretty bright during the initial burn, so that should help cut down my exposure time.
What tips do you have for me?
EDIT: Thanks for all the suggestions. I thought I should share my results from the bonfire. 
To give scale here is a before shot:
And during the burn: 

A:

I would shoot series of identically exposed shots with tripod, underexposing them enough to not blow the highlights on the flames too much. Then you can stack the set either manually or with programs like Anti-Lamenessing Engine (ALE) to get the surroundings parts properly lit and then use layers and masks to pick flame part from some single frame.
In situation like this, where the subject changes wildly, hefty stack of exposures with identical settings also gives you lots of frames to pick flames from, so you can handpick the version of flames you like most, or even combine it with couple of frames with layers and masks.
Developing with different settings from same raw does not give you any more signal than just converting the same raw to 16-bit image, so there is no real use on doing that, unless you are using photo processing program like GIMP that lacks support for 16-bit images.
Shooting the "normal" HDR stack, ie. set of 3+ images with exposure bracketing has the problem that if subject changes between the shots, like it certainly does here, you easily end up with ghosting. With identical (underexposed) exposures you need more shots to get enough information, but the ghosting in that methods turns to just regular "motion blur", which is more pleasing to human eye.
Also, flames are bright and self-illuminating - if your plan is to capture just the flames, a single exposure might very well be enough. But because memory card space is cheap, shooting couple of series from tripod will leave you with lots of material to choose from.

A:

Pulling out multiple JPEGs from a single RAW file always results in lower quality HDRs than the one done with bracketed RAWs. Specially the dark parts of your image will show noticeable noise. On the other hand, bracketed shots require static scene which isn't the case for you but I believe is the right thing to do. If I were you I'd shoot as much bracketed shots as possible and try playing around to get the best outcome. Flame shots at night typically ends up requiring 1/30-1/40 (considering you already have some fast enough lenses) shutters which will not stop the action to a full stop but wont be bad either.
Worst case, when merged, resulting HDR will show some crowd movements and a dreamy flame, which isn't bad either, in fact it will add some interest in the photo ;)

