I just wanted to report back since this past weekend is the first chance that I've had to ride this bike again. I tightened the chainring bolts as you suggested and it certainly quieted things down quite a bit. While not completely silent it has reduced the creak by a good 85-90%. I need to give the drivetrain a through clean and lube and hopefully that will take it the rest of the way. This was absolutely a creak, not a rub. No cross chaining.

Thanks for the tips.