Delta Skyclub. The Centurion Lounge is decent, but it's often really crowded and has a limited food selection. Since you have 2 guests that poses a bit of an issue since it would cost you ~$60 each way to bring your guests into the Skyclub so in that case you may want to stick to the Centurion since there is no cost for the 2 guests. If it were me travelling solo I wouldn't even bother going to the Amex lounge and just stick to the Skyclub. "The Club" lounges kinda suck, and the Alaska Lounges at SEA are leaving Priority Pass effective Sept. 1.