Well, I knew I shouldn't have said anything! Last night, Tgirl was up off and on until after 11, crying and being miserable. Then she was up at 4:30 for the day. Not to be outdone, Tboy woke up at 5, although I think we did manage to get him back to bed for at least 30 minutes.
Lesson learned: next time things are going well, just don't say anything!