A single character boosted all the way to level 80.
A free upgrade to Cataclysm, regardless of the expansions you already own.
An optional free character move/faction change.
7 free days of game time.
The person sending the Scroll gets one of the new mounts for free (the star pony reskinning of the basic faction flying mount).
Looks like a pretty good deal on either side. See more details on the offer and picture of the mounts here.
If this is enough to make one of you want to come back, I'd love to