Currently I use 30D with 17-40 and 70-200. Basically take pictures of daughter doing goofy things. Last weekend, we went to zoo where the 17-40 was perfect. I would have liked to take more pictures of animals using 70-200, but lens swapping was a huge pain. And there was a healthy breeze so was paranoid about getting sand/dust into camera. Would you use two cameras in this situation or just swap lens continuously? Maybe an XT or XTi? Was saving for better tripod - my current WalMart model makes me nervous when I have the 70-200 mounted.