The correct way to do this...
Create two arena teams, use two accounts.
Account A has a char that makes a team, Account B makes 4 chars to join it. Have them all join his group and then ALT-F4 so they don't leave the group.
Account B has a char that makes another team, Account A makes 4 chars to join it. Have them all join his group and then ALT-F4 so they don't leave the group.
Have Account A arena leader open and Account B arena leader open. (Dual Log - I recommend windowed mode)
Have them both queue for 5v5 at the same exact time. If the queues pop together, bam. You're in. Easy badges.
Easiest to do when not many people are online, so try to do it early morning (5AM) server time.
I have a very powerful computer, so I made 5 accounts for Team A, hehe, and geared up 5 characters at once. (That's six WoWs running at once) A few days of this and they all had the best gear/enchants possible.