So I am thinking about getting a CO2 tank. I am thinking about getting a 20 lb tank and splitting it 3 ways with the other guys I jeep with. So now here is my question, If I were to get the tank, would I be able throw this bad boy (see link below) on as well and be able to air up all three jeeps at the same time? or will the psi drop too low?

3 Way Air Hose Manifolds Brass Quick Couplers 3 Way Quick Connector | eBay

 

Tank- 20 lb. Aluminum Co2 Tank | BeverageFactory.com

Pressure Regulator- Poly Performance CO2 Fixed Regulator

add any hose and air chuck

 

I would get your own and be done. Sharing could be a pain, the line would be all frozen by the time your done with everyone and could damage to it if you do that all the time and are not careful. Frozen things break easier I think.
The bigger issue would be your tank would run out far more often due to doing 3 sets of tires each time so you will be the one making trips to get it filled. Maybe your place is close you can fill up and its not a big deal? The key on a good setup is the regulator, don't skimp on that, because the better you get the more flow you can allow and fill tires faster!

Here is a picture of my tank mounted to the roll bar when I run the daily tires.

 

I would really reconsider the 20# tank. I tried that for a while but it was just way too big to mount anywhere. I'm much happier with my 10#. It fits right where the stock sub woofer used to be and I can run hardtop, soft top, or frameless top (with the 20#, I wasn't able to use my Trektop because the tank was too tall. The only place I could secure it was strapping it behind the rear seats with a strap to the headrest and another to the floor anchors.
Edit: I've seen a few people like Brute4ce(?) with 20# tanks, but most of them have custom brackets.

 

I have a 20# and wish I went with a 10#
If you go to a beverage supply or welding supply co they will want to do a tank exchange so you can start off with a 10# than go to 20# if needed. Don't skimp on the regulator cheap ones will freeze up quick.

 

I have a 20lb tank. mounting is not an issue, assuming you are ok with having to remove it to fill the tires - mine is mounted horizontally in a powertank bracket on my tuffy deck lid (JKU). I swap my tank out at a weed growing store for $7 and have a fixed pressure regulator. don't share, they are cheap and your line will freeze.

 

I wish that I'd have gone with a 15 or 20# tank versus the 10#. One thing I have learned is you get what you pay for so when my cheap SmittyBilt regulator crapped out within a year I knew it wasn't money well spent.