#3 is a good option to go with. I might even say take it a step further and do 2 priests 2 locks. That way you can keep one priest for healing, and then have another to spec as shadow. Shadow priests and locks synergize way to well to ignore, if you ask me.

Really as far as CC goes, if you're good enough and geared enough you don't even need it. Especially with pally tanks since threat shouldn't be a problem. There are people out there running heroics with a 5x shammy group (Veronika I believe? There as some videos in the videos section). If you can do that, you can probably run about any team, as shammy's have no cc really.