We've often noticed those families that are so active they take the bikes with them. So we got one of those things and we did it - just the once. It made me nervous thinking they might fall and the bikes didn't really get used enough I fear.
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.