Welcome, I think you would be happy with a JKU purchase. I've two little ones and they really enjoy it. The back seat is a little upright, so the car seats sit a little vertical, but I just read someone on the forum change the angle of the rear to make it tilt back a little bit. They could've make a little more room back there, but its not that much different than other cars we've owned w/ the carseats.
We get 18-20 with out manual x w 3.73 gears, and I've put some step like rock rails on for both the protection and for help with the kids getting in and out.
The hard top is suprisingly quiet, and the freedom top is nice when the you want the top off and the kids dont.
You won't be disapointed!