Since you're going to walk right past the kiosks on Discovery Island on your way in the park, I'd take the 2 minutes to look quickly and see what was available for SDFP, especially since you've done it before. If there's a kiosk anywhere near Everest, I'm not aware of it. So I think you'd do a lot of backtracking, plus I think the time you'd take to look for SDFP would have far less of an effect on the line at Everest at that point (this might be different if you were talking right at ropedrop vs 15 minute later). But I think the time it would take you to walk to Everest, wait in line, ride, and then get back to a kiosk would have a major effect on what availability remained, especially if you're looking for earlier in the day.
Thank you! I think you helped me two years ago, too. I remember that cute photo in your signature. I will take your advice.