Yes its better to shoot low light photography in raw format as it captures a great deal of digital information that allows you to recover significantly more exposure values than a jpeg would. Use as fast a lens as possible is also a good idea (Nikkor 50mm f/1.8D is a good and inexpensive choice, just bear in mind its limited field of view and inability to zoom). Raising your ISO up will also help but, just be aware that the higher the ISO, the more noise will be apparent in your pictures. You can remove it to a large degree in post processing but its not always 100% successful.
I'd recommend doing some test shots on the day and get your ISO up as high as you can without the noise becoming a factor. This will in turn help to raise your shutter speed and reduce the chance of motion blur. If you're using flash, this isn't going to be so much of an issue. Bouncing the light off a white ceiling or wall will help diffuse the flash and create softer, more even lighting, with little to no hard shadows on walls.
I can't say I've heard of Digital Concept although I have heard of Quantaray, although never used any of their stuff. I have a Metz 58 AF-1 flash gun, which I can strongly recommend. I think it came top in its class when it was launched, even topping Nikon's SB600. The new AF-2 version is out for a touch under £300. You can still get the AF-1 version though. SRS Micro Systems have it on sale for £215!! About £45 cheaper than I paid for it not that long ago