To be safe, you'd want to go to the Delta iDine website and remove the card from your profile. But you may have a problem here. I think the Delta Amex can only be used for Skymiles with iDine.
Some affinity cards actually come preregistered to earn miles with iDine - that's what happened with either my BA Visa or NW Visa, I can't recall.
You may want to call iDine customer service on this.