Devotions are most certainly ecclesial life. You cannot take CCC 1669 in pieces. Read it in full: the laity may preside at certain blessings. Not all. To know what those blessings are, you must have the Book of Blessings or Shorter Book of Blessings. The rubrics explicitly note if a layman is authorized for any given rite.
The blessing of a home is a good example. Because it calls down God’s blessing on the home as a dwelling, but does not set it apart (as one would, for example, a monastery), a layman, preferably the father of the house can preside over blessing it. So, for example, is the St. Blase blessing of throats: laymen are permitted that blessing as well. Parents most certainly bless their children, and family members can bless their sick loved ones, outside of a sacramental rite.
But a layman cannot bless, for example, a St. Benedict Medal. The Book of Blessings grants this explicitly to Deacons or higher. A layman cannot “make” Holy Water. A layman may most certainly ask for God’s blessing on a candle or image (Lord, bless this image…) and that most certainly counts for something. But it does not make it a “blessed object” in the same way it would be when blessed by one with the authority of Holy Orders. And he cannot use the rite of the Church for blessing objects of devotion, which is reserved to clergy. I did not bless my own Breviary; I took it to a priest for his blessing because the book is specifically set apart for a sacred purpose. A lay person can only pray to God to bless the object; a priest would actually use his authority to impart God’s blessing on it and set it apart.
Articles of religious devotion (a Divine Mercy image would fall under this category, as would crucifixes and icons) are also blessings reserved to Deacon and higher. Again, one may pray in his own words for God’s blessing over it, but cannot bless them on his own authority.
And for all his lack of learning, Francisco was right: today, as in 1917, only clergy can bless Rosaries (SBB n. 884).