This was asked almost word for word a few days ago here:

Dual-box'ed Druids Suggestions

My comment from that thread (which is on the 2nd page atm):

People generally prefer to use ranged casters since the positioning is easier than multiple melee.

2 ferals will never ever need to sit down and drink, only the occasional heal. People doing multiple melee generally run their main toon through the mob so the followers get into melee range and get back shots. With alternating shreds you'll get some aggro pingpong and very fast deadness.

Boomkins destroy things but they drink a lot (like some members of my family). Once you can get them into boomkin you'll want to use a friendly mage (yours or someone else's) to load you to the gills with water before you head out.

You won't likely need resto tree until you're in the 60s and that's more to get experience with resto spec more than anything else, because tree healing is different from other healing.

You also could only swap one of them to boomkin at first and see how you like the synergy. It could be great or it could be annoying with the chicken constantly pulling aggro.