Little bit of advice needed

You're going to need a good local CO2 supplier. Youc an either go to a hardware store and fill up your CO2 tank each time it's empty (which, depending on how far in the woods your field is, could take some time an interrupt play), or if you guysd are VERY serious about this, get a CO2 scale and fill station, and actually bulk-purchase the huge tanks of CO2 they use at fields. Also, you're going to need a lot of paint. With 20 people, if you can pool your money, you may be able to bulk-buy it wholesale.

Many retailers will offer 'field packs' of markers, say 10 or 20 98C packages all together, at a serious discount. Take advantage of these offers if you can find them.

Get some spare parts kits for the 98s. Even though they're tippmanns, with that many you're bound to end up with a few problems. Get lots of o-rings.

Good luck in your endeavours. Hopefully if thigns go well, a few years form now you guys may find yourselves setting up a business with the land and gear you've got. Speaking of the land though, find out who owns it, and make sure you can play there.

 bye draxxus paintballs they're the best

Yes, you can mount a scope to a 98c.  The line you are referring to is called a "remote".  They cost about $20-$30.  You will need a harness that has a spot for your tank.  A 4+1, 6+1, or 8+1 depending on how much paint you want to carry with you.  If you don't have the money for a new barrel right away, you can take a piece of electrical tape and put it over the ports on barrel (the ones in the middle of the barrel).  This will help improve on accuracy and air consistency.  Just remember, the longer the barrel, the more air you need to push the ball out.  The flatline is good but, you lose accuracy (depending on the wind).  You may want to look at getting a chrono so you don't have to worry about people shooting over 300fps (big safety concern).  Remember to think SAFETY FIRST.

If I had the money when I started paintball, I would have bought the A-5 b/c of the cyclone feed system (almost guaranteed not to chop a ball).  The only time I chop with my 98c, is when I try to shoot over 10bps for more than a few seconds.  A fast hopper would fix this problem.

Good luck.