Adolfo,
Let me know when you are going to go and I will see if I can meet you (if it is on a weekend). That fall migration is supposed to be stellar, place just crawling with raptors.
The places to set up are boulder outcroppings, so I think you would go crazy trying to shorten legs and finding good places to put the tripod. There are a number of different places, but all involve climbing over/around a few man sized bounders and I wouldn;t want to deal with a tripod.
I ended up climbing out farther for better views and cradling the 70-200 in my lap. Though I bet a monopod would work.
Now, for a monopod, I think a ball head is overkill.
Check out the RRS site for their suggestions for mating a swivel joint to a clamp for a monopod, I think this is better. You can twist the pod from side to side anyway, all you need in a head is to control the elevation of the lens
http://www.reallyrightstuff.com/tutorials/monopods/index.html
However, since I don;t use a monopod or a big lens, I would get some more learned advice before worrying. Just the big ball head seems like extra weight and hassle you may not want, though it's nice to have a tension adjustment for easier movement of the lens once you get in place. That alone may make the ball head preferable for tracking fast flying birds.
Now, when I went there I left almost ready to burn the CC for the 200-400. Whne you photo birds I think you jsut want length all the time. If there was a 800VR for $10k I would want that, etc.
So, yes, bring the big glass, esp if you want close ups. The pic I showed was at 280mm, and as close as I expect you can get to a bird unless it attacks you personally. Behind and above you are trees, so they cannot really get right on top of you, and this was taken at the end of a rocky outcropping. So, I would consider a 200-400VR WITH a 1.4TC if possible.
Of course, with your D2X you can crop a lot more and retain detail than I could with this D70 shot.
Throw the 12-24 uin your pocket for one or two close ups, and it you want ot save on weight, skip the 70-200 (I cannot believe I am saying this, as I love this lens above all others, but I don't own the 200-400)
I have never tried, but I wonder if a fill flash with somethign like the "Better Beamer" might yield better results.
Finally, if you feel overwhelmed I will meet you and use your 200-400 for you, giving you full credit for any photos.
I was carrying my 70-200 and 17-55 and glad not much more. I also almost lost the 17-55 out of my bag while going over a rock outcropping, which really put the butterflies in my stomach. If you are bringing all that glass try to bring along a friend or the wife to help you tote and port things around rocks (ie, hold this steady please while I jump down and then hand it to me)