Faster way to level my group

I am currently leveling a group of 1 pally and 4 shammies by a combination of instances and questing. All are pretty low level (24). I wondered if it wouldn't be faster to replace the level 24 pally in the group and replace him with my level 67 pally instead. The question is would the experience loss from having a high level char as a part of the party be offset by the ability to go into areas that I couldn't go with the lower level group?

Thanks in advance for your thoughts.

no. with your setup you will walk through most areas pretty easily.
with a 67 pally to help instead of the lowbie pally, you should just do instances.
1. no outside interferance.
2. mobs stay glued on you until you leave the instance (mostly)
3. you get more exp per mob.
4. you can reset all instances 3x per hour.

so do two or three instances. heck hit up SM, all four wingsx3 every hour. easy.