Thanks all for the info, I am at about 60% through 79 now and so I will probably hold off on any dungeons until I ding the whole team now.
My next big decision will be whether to run some regular dungeons (HoL or UP) before trying to do the heroics or just barrel into some heroics and see how the tank holds up. As per a different thread, I may just drop in my pally tank instead of the druid to gear up the team or even possibly drop in my resto druid to see if he can keep up the heals on the newbie tank.
With the priest I think I could gear her pretty fast from crafted epics but on the other hand I do not want to have to waste gold on epics which I can get from badges!
Looking forward to trying some of the above comments