I don't know about Eyefinity either, I don't use it.
Assuming that it can be done, you will probably have to capture a huge amount video data, and need a tip-top system to capture it at a good frame rate. You would probably have to compress the data on the fly, to a more lossy capture, a lower bitrate. This doesn't make it a bad or poor video, just because you lower the bitrate.
It's a question of balance, RGB or almost lossless capturing mean you need tons on space and pretty fast drives. Using a bit of compression means that you will use some of your CPU power to do the compression, but save a lot of disk space. Finding the balance that will work for you will take time. If you have a good capture program, then at least you will have a choice of codecs to choose from, there isn't a choice with FRAPS.
Currently I use a medium quality codec without additional compression, which I can enable if required (YUV420), there is YUV24 above it, and then RGB (True Quality) itself. The low quality YUV (but still good), is YUV410. A great lossless codec is Lagarith (a free codec).
Using my 'medium' codec I capture games @ 1920x1080. The bitrate of the resulting files are roughly 730 Mbits. When I compress them later to x264 mp4 or mkv, I compress them to around 12 - 14 Mbits, this is still a reasonably high bitrate, which will be further compressed by you-tube if I upload, to around 5 Mbits (HD)
At my capturing rate, that 730 MBit video takes up around 5.5 Gb per minute of disk space @ 1920x1080. So a typical short 30 min MP race with friends @ 30% race distance will take around 165 GB of drive space. So you can imagine what size the file would be using RGB True quality recording.
Of course it is all going to be multiplied again, where assuming you are using 3 HD screens @ 1920x1080, you will be capturing at 5760x1080, a gigantic number of pixels to capture, store and/or compress on the fly.
Don't let me put you off, but I think you may have a bit of a challenge on your hands, trying to balance system resources, game performance, and video quality.
Good luck
EDIT: Just to make it clear because it isn't in the above text. YUV & RGB are colour spaces not codecs, YUV being more lossy than RGB. It's a combination of codec and colour space. In the above text I use the dxtory propriety codec, Fraps has it's own codec, so does Playclaw. With most programs you can select different codecs (if you install them), MJPEG (Motion JPG) is common, and Lagarith is a brilliant lossless codec and is compressed, which saves space.
