Which lens to take?

Here is the scenario. Dark horse arena with two awfully bright openings. Dog confirmation classes. I walk around, no tripod and no flash. Take photos of dogs being shown from OUTSIDE the ring. Take a lot of candid shots of people being happy, sad, or just funny and dog's faces.
Here are examples. Please disregard quality of photos below. They are posted just so you can understand specific scenarios:

it greatly depends how close or far you plan on being at. I have gone to a dog show, with a 24-70 front row, but ended up changing over to the 70-200 f2.8

Shot with a 24-70 + flash 1/50 @ 1600iso

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You're going to need the 70-200 f/2.8 for the inside shots as you've described them. Sell the 70-200 f/4 and add what you'd spend on the 24-70 f/2.8 to get at least the Sigma 70-200 f/2.8, possibly going all-out for the 70-200 IS. If you can't get the IS, consider working with a monopod. Jack Russell Terrorists^h^h^h^h^h^h​iers aren't large enough that you'd have any coverage except from right on top of them with the 24-70.

given your situation the 50/1.8 is necessary for candid shots and the 70-200/4 shooting at 1600 or so should help you out. use noise ninja in post production to smooth out the grain.

if not splurge on the 200/2.8 L (still, its 600$). if you're going to shoot out at the 200 range on the 70-200 most of the time, the 200/2.8 will be lighter, easier to handhold, less intrusive than a big white lens.

My 2 cents

typically 20 - 150 feet.

JRT trials are smaller events - almost always taking place at the fairgrounds. I have been already to 4 this year. Many more in front of me.

If you have time and nothing else to do , here are examples of the slideshow I make from all the shows and give to my friends attending them. They like it - they bring good memories. I feel like reporter creating picture stories of the trials. I just got so frustrated not being able to take shots in these dark dark places:

confirmation:

http://www.photoshow.n​et/watch/MN9Ku4ma

racing:

http://www.photoshow.n​et/watch/XN3ak8Ma

I have JRTs and the first shots on Saturday after getting my 30d on Friday were of my pups. Here is one:

use the 70-200 and up the ISO
Or if you do want to spend money get the 85f1.8, great FL for candids on the 30D and fast

For the images you desire, the Canon 70-200 F/2.8 L IS would be the best choice.

I realize this is a very expensive lens, but you seem to want your lens to respond to some very challenging conditions, specifically:

No flash
Poor lighting
Frame filling images from rather long distances
Low ISO quality

The lens cited above will handle most of these challenges, but the lack of wide-angle coverage will frustrate some of your desired images.

Bottom line, I don’t think one lens will provide all the usability you desire, but the Canon 70-200 F/2.8 L IS will get most of them (it will leave you wanting on the wide end).

Another good choice might be the Canon 24-105mm F4 L IS lens (this lens will leave you wanting on the long end).

Enjoy! Lon