I like to handle Christmas by plunging straight in there fairly early on with sermons on the incarnation and lots of Christmas hymns. We sang 10 yesterday and I preached from Matthew 1:1-17 and Revelation 12:1-5. The morning sermon is really the beginning of a new series on Matthew (I plan to look at the rest of Chapter 1 next week). I got the other text from Roger Ellsworth. It's a rather less obvious Christmas text. We had one or two visitors which was good. We also had tea together before the morning meeting, which was nice.
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.