thats a great team combo. A priest or hunter instead of the ret pally might be slightly better, but only marginally so. The better geared your tank is the easier time you will have in heroics, if you can farm a few k gold over a few days you can buy all the tempered titansteel and a few BoE epics and easily push 25k hp in frost. Farm gundrak/draktharon first, they are the easiest. signet of the accord is a great tanking ring that will last you a long time, tempered titansteel helm also lasts a very long time (my DK is in full naxx25/ulduar gear and still has it... bad rolls on kt helm qq)

The trickiest thing for you will be the bosses that do AOE team damage, you will need to write macros for your druid that can individually heal any party member quickly, another that can group heal, and of course another that heals just the tank with big heals. for example F1-F5 to heal party1-party5, F6 to heal tank, and F7 to throw a group wild growth. Those keys should do nothing on the rest of your team, they are just your heal keys (can use numpad, shift-keys, whatever)