Well, that went better than I'd feared. Nicholas actually slept until 5:45 a.m., then wandered into our bedroom and crawled in beside Daddy, where he spent the next hour wiggling intermittently, but otherwise staying pretty quiet. So I was able to doze until just after 7 a.m., which worked fine for me. (Though for Daddy, not so much.) And today Nicholas seems more like his usual perky self.
So we're all getting back to normal -- slowly. Thanks to all of you for your commiseration and advice.