I opened a Saks card but did not make any purchases that day. Then about a month later I was at a Saks that did not carry Chanel and I wanted to make a purchase. The associate just called another store, told them it was my first time using my card, I received the discount and she sent me the bag. I think the Saks system knows that it is your first time using the card and automatically takes the discount. If not, the SA will check, and then give you the discount. To summarize, you get the discount on the day that you make your first purchase, regardless of the day that you open the account. And, just tell your SA to ensure that your purchase from the other store is rung up on the day of the event. Then you will have no trouble receiving the discount.
As for your question regarding the expandable bag. I'm not positive but I'm pretty sure you cannot pay for a bag that they do not have in their system. So if the bag is not yet available, I don't think they can charge you for it. Therefore, you will not get the discount, since the purchase must be made on the day of the event. (I hope this wasn't too wordy.)
