My suggestions, based on leveling a rogue+priest combo with my wife...
Go shadow and MS/Fury and just beat stuff down, tossing heals as you need. I wouldn't worry about instancing unless you guys are just looking to have some fun and take it slow.
I leveled my warrior as MS and had no clue how to tank when I hit 60, but I learned in 3 runs of BF how to hold aggro very well, and since then I have really improved.
Basically, I suggest learning in the 60-70 instances, and getting there as fast as possible.