Just a thought here... if you can't kayak fish due to back issues a 18' CC is exactly the last thing you want to get on. I've had the shit kicked outta me on my 23' plenty of times and it's a heavy ass boat.
Also I don't think it's going to be big enough with three anglers and two boats. As mentioned by another poster, racks would have to be beefy to sustain the pounding but also not rip the gunwale of the boat when you get douched by some a-hole's wake.
Here is my rig with two BWE members PA14s when we went to the 'nados. Sucked on the way out becuase I really couldn't see well to port. On the ride back we just stuck both PAs over the transom with the bows on the bait tank. Worked way better but didn't have much room and couldn't take leak over the side.
I'd say something like my 23' or a Skipjack 24 minimum. Just for the sake of your back man. Heavy is good when it's full Victory at Sea and you're down at the 1010.
Anyhew... my $.02