well i'm no longer a CM, so i don't feel the need to uphold every secret. And many things are discussed more than they should be in certain topics. And dining discount is one of the few sharable discounts. Meaning that as long as the cast member is present at the table any one can pay for the meal. But the discount only applies up to the number of people on the maingate (which is generally 3 additional people). Merchandise can only be bought by the cast member for the cast member, they may however gift you the item.
BTW, the holiday celebration discount has changed. It's no longer the two coupons.
And there are plenty of blockout dates too. If you want a discount on your food, you might want to look into tables in wonderland card, there are no blockouts, no limits on where it can be used, or automatic gratuities. It's a lot more verstile than a castmember. And if there are lmits, it's a lot less limited than the CM discount.