Sorry to say, but just adding height to the tank wont be enough, especially with the amount of the footprint that will be taken up with the water area. They need (for a tank with just ONE dragon) twice their length long, once their width wide, and twice their length tall. Generally that is a 6'x3'x6' enclosure, just for one. Two or more will need a little more room (shouldn't be too much more, maybe a couple all around, or three feet longer and a foot higher and wider). I know you said you don't want to know about their care, but this is about their care, AND about the cage.
I would be careful not to get too many juveniles at once, as they will quickly crowd the tank as they grow. They will also fight once they reach a certain age unless you have all females, or only one male and the rest female.
That said, much of the questions you are asking have been addressed before, so please take some time to read through the threads (both in the vivarium area and the lizard area, as there are CWD specific posts dealing with equipment and such in that section). The search button is also very useful. If you still can't find what you need to know, feel free to post a new thread, or ask for more info on a current topic by posting on an existing thread.
Welcome to the forum, it will be nice to share ideas and experiences with you.
