Hi Smdecuir, All!
Some Oak leaves are toxic; Red Oak? Other than that, I've seen my (very well fed) critters happily munching on the new Scrub Oak (Gambrel Oak) leaves and branches, so I doubt they are _too_ toxic. Check with your local farm annex for a definitive answer.
I keep the water bucket right at the faucet, and top it off at least twice a day. I would suggest keeping it as close to a faucet as practical, if for no other reason than to save from messin' with a long hose every time you need to service it. Make a custom hose that is just the right length. Another thing to consider is a location where an Alpha animal can't bully the rest away from it, and where it can't easly be tipped by them "horsing" around.
I wouldn't worry about the water temperature too much; they'll drink when they are thirsty regardless; just keep it clean and full for 'em. If they want cold water, they will come up for a draught while you are filling it :-)
PS, in really hot weather, mine just love being sprayed with a hose. Just like a bunch of kids, I tell ya!
Steve Jernigan KG0MB
University of Colorado