First post on OP. I've been a magazine subscriber for years and learn from every issue, just love it, thanks.
I'm shooting with a 7D in HD using 2 lenses, an EF 28-135mm and EF100-400mm. This goes on my kayak or canoe in a Pelican waterproof case. When I'm shooting I put the strap around my neck and push the camera away to stop camera shake.
Just bought a Hoodcrane cinema kit with loupe, this makes it more like a video camera and is a must have. In the canoe I take a tripod which is even more important for shooting video. Recommend a small tripod to take with you on the kayak for shots from the bank. If you don't use a tripod you will lose most of your footage. You won't be able to pan, just set the camera up and let the action flow past. I've tried a monopod, poor video tripod, carbon tripod with ballhead and high end fluid head. I now the limitations of each quite well by now.
The camera mic is horrible, so you will need a camera mounted mic. This is a whole new learning experience and not a bit like the normal use of a video camera, but the results of the HD are truly fantastic.
We can shoot all morning with a 16 gig card and have a spare 16 gig card and CANON (do not buy the knockoffs) battery. There are definite limitations such as overheating and stopping at 12 minutes or 4 gig. You get to know the camera and work around this. Also consider a 5DMK11 which has a full frame sensor. I love my 5D, and bought the 7D because of the video capability.
DVINFO.net has a forum on the 7D which you will find helpful. You will need plenty of practice with the camera before the trip. Don't forget the cost of editing, we needed a new computer, upgrade to 64 bit, CS5 Premiere Pro, sound editing software etc. There's no inexpensive way around that part IMHO.
I'm adding a blog page to my web site and hope to post useful stuff as I get the time.
Good luck with your trip and every success with the filming.
Canvas Print Service for Nature Photographers.http://www.BaileyNatureGallery.com