Welcome to the forums man, its great so another oldschool player around. I remember day 1 of live, it was a fucking nightmare on blackrock realms down queues as long as 1000, but things have changed and i dont care what people say blizzard are doing a good job managing the game, even though alot of there micromechanics are a bit stupid it seems, the game certainly has come a long way and we can see that. I decided to start boxing for the same reason, I was bored raiding after doing it for soo long and my guild wasnt progressing at the speed I thought it should be. So i thought i'd scrap it and try a style of the game that ive never had a chance to play in the past 3 years or however much time ive wasted on this game:P

Its kind of hard to think of how to break your groups up, but think about your specs first.
A general tip that alot of newer boxers need to understand is that boxing more than 1 melee class is considerably more difficult than doing a few casters, healer and so on. So maybe consider your pallies as either your PVE tanks/Heals or PVP healers.
This reason is because of autoattack at the follow distance can be upset and the character on follow wont always be in range, so there is a bit of twinking and fucking around each time you goto attack, well thats the problem i found.
Your in a bit of a different situation than most boxes and i will bet which ever way you go that you will regret and want to be swapping chars between accounts often:P
Dont forget, depending on how well you can handle it and work with it, if your guild is forfilling enough you can take a few chars on raids next time. We've seen Ellay's 4 shamans kill vashj not too long ago, and 2x5boxing kara. So there is more potential to go further than heroics in the PVE sense
GL with it man I really hope it works out well for you, i can guarantee that you will enjoy a change to your normal game that your playing each day, an new refreshment to come home to and enjoy.
PS what realm are u from