If there are 6 people at your table you'll be charged an automatic 18% gratutity at WDW. Even if 2 of the 6 are sleeping infants. Even if you split the bill 3 ways, each bill will have an 18% gratutity.
Many on these boards seemed rather paranoid about this new policy at WDW. However, this is a pretty std practice at restaurants, just check the menus. For some its 6 for others it is 8, but an 18-20% auto tip for groups isn't odd.
Some of us will get good service, others better service and sadly some poor service. However, if its poor, just involve a manager early to get things resolved.