The Pro system is excellent, you should definitely look into that as MiRai says. Follow his videos to set it up
https://youtu.be/iqHaH4gbrmoHaving played a bear in retail, I can say it's really easy to set up. Make sure your talents all help to make the rotation simple, i.e. prefer passive talents and don't take pulverize or galatic guardian. Then you can set up the Pro System, and give the character who is the bear a separate virtual key map.
In that virtual key map make a mapped key called "Easybeartank". Make it send
all the following keys to the bear
in this order: Wild charge, Thrash, Mangle, Ironfur, Swipe. So you'll have 5 actions in Easybeartank. When pressing all the keys at once, ISBoxer does actually send them one at a time, so the WoW client will always see the keypress for e.g. Thrash before Swipe.
Now for all dps bindings you make for the moonkins, in the corresponding mapped key on the bear's virtual key map, just call
Do Key Map Easybeartank. This means, that whenever any of the moonkin casts anything, ISBoxer will send all 5 tanking buttons to the bear. When the moonkins cast moonfire, you might want to send the moonfire binding to your tank as well, but I found it's not necessary to keep threat. Once you get used to the system you can add your defensive cooldowns like barkskin and regen.
Healing is another matter. You will need to add some macros to put your toons back into moonkin form after a heal. But I think once you see how handy the Pro System is (with some practice) then you'll have no problem changing one of the moonkins into a proper healer, or even a cat-healer casting free regrowths from predatory swiftness.