Honestly, I wouldn't waste money reupholstering these sofas unless they have some sort of fatal damage. Put some Old English on the legs to cover up the scratches. Suggest you paint your walls - maybe a nice soft "villa" pale yellow. Invest in a decent patterned rug & get some throw pillows to coordinate. Move rug & sofas to face the fireplace. Move the TV to the corner where pic is oddly propped in photo. Drape the table to cover up all the wires. Move the bookcase to wall where larger of 2 pics is located above. Put a plant in your pot & locate it next to the bookcase.

Sorry but your art clashes. You need to either keep the one large picture or the other 3. If you keep the two smaller ones, hang the smaller above the larger where the one big painting is now. If you keep the large one, you will need to lower it about 10 inches after moving the TV. If budget allows, get a better coffee table. I hope your dogs are all "fixed"!

Why spend the money if they are in good shape. With 4-5 dogs, might be better to just re arrange room. Move sofa ( by the way I like color) to look at TV wall. Buy nice media center, or go to antique store find a buffet and use that on that wall with TV on it. You might go bigger screen 50". Move big art from over TV to wall that has sofa. Remove all other art. Remove book case. Replace area rug same size but a red print. Add two brown leather chairs on wall with sofa now with table between with lamp. I think room would. Be more functional, cost less than new leather. With more seating. Also very dog friendly. Top grain leather always. The heavier the grade the more study. The leather chairs can be what is called distressed, which would solve your problem, of toenails. Change is good.

Why do you want to redo the sofas? Maybe it is just the inside "stuffing" that needs a boost. In your pic, the leather looks beautiful. I found one website that explains the leather thickness this way:

As a general rule, each ounce of thickness is roughly equal to 1/64 of an inch in thickness.
As an example, 8 oz leather is 8/64" thick, which is the same as 1/8".
Some simple examples of thickness based on US coins:

A dime = 3 oz
A penny = 3.5 oz
A quarter = 4 oz
A nickel = 4.25 oz So, dig this: 6 oz leather is like two dimes stacked one atop the other.
http://www.brettunsvillage.com/leather/conversions.html

I also found this site that speaks about yardage needed:
http://hidehouse.com/forms/catalog.pdf

The room actually has two red leather couches. Here is another picture.

Processing will factor. The best quality leathers will be full grain (not top grain) cowhides w pure aniline dyes. These make up a small percentage of the products available, but wear better and longer.

In regards to reupholstering leather furniture, Is it ever a good idea as I think cost would be prohibitive? I have a mid century stressless chair that needs either reupholstering or selling? What is the consensus?

It is a good idea - when a particular effect is called for in the design, or when a piece is beloved, or when period styling is calling the shots. The wearability is a huge factor for those who love it, and the cost is rationalized accordingly.

Studio10001, are you an upholsterer? I ask because a top grain leather can be either full grain or not. If it's not full grain, then it has had something done to it to change the grain, so full grain is not a grade higher than top grain. That's my impression anyway. I could certainly be wrong which is why I am asking.

The leather on my sofas is starting to crack that's why they have to be redone.

Top grain is a misnomer: it involves removing the top surface of a hide and then restamping an imitation grain for uniformity. This process also reduces fiber strength and natural moisture resistance.
Full grain is the real top of the leather heap; it has no such sanding processes, shows hide irregularities and is therefore designated to better quality skins to begin with.

Have you spoken with a leather expert about compairing what you have? I put leather conditioner on mine to moisterize it and it seems to remain soft and not brittle.

If what you have had held up well over the years I would ask for that again since the environment (animals) is not the only consideration. I once had really high end Italian leather sofas that felt like skin. I'm not sure how well they would have held up to dogs. We did not let Sam (Great Dane) on them but they were dreamy to sit in because they were so buttery soft to the touch.

The leather I have now was bought to hold up to kids and 8 years and a small dog continually using them and they still look and feel great other than one small scratch a visiting dog put in the foot stook (they recline).