Can lay people give blessings at Mass?

Answer: NEGATIVE
Authoritative: YES

Unfortunately, the presence of Extraordinary Ministers of Holy Communion has become ubiquitous in the Novus Ordo. That being the case, there is a good statistical likelihood that on at any given liturgy you have a 50-75% of receiving Holy Communion from a lay person, depending on the geography of where you happen to be sitting. Aside from the obvious concerns about lay people distributing communion and the universality of "Extraordinary" Ministers, there is another issue that this phenomenon brings to mind: the question of lay people conferring "blessings" on people during the liturgy. You know what I'm talking about. Your child goes up to communion with you, and despite your best efforts to shelter the child at your side or out of reach of the EMHC, the EMHC reaches out, puts her hand on your child's head and confers a "blessing."

Those of us who consider ourselves traditionalists know that this is just plain wrong, on many levels. But for the cynic, for the progressive, for the clueless Mass-goer who might not know the rules and does not see the problem with this sort of thing, can we bring forth any hard documentation to prove conclusively that lay people are not to confer blessings at Mass?

Why yes we can! In a letter for the Congregation for Divine Worship and the Discipline of the Sacraments from 2008, we have the CDWD teaching clearly that lay people not only should not confer blessings, but are actually "unable" to do so, as this is a specifically priestly function. The document cites the Roman Ritual De Benedictionis (On Blessings) no. 18, which is where this is authoritatively taught. Here is an actual copy of the letter with the relevant citations:

As a secondary issue, note that it says the blessing in the form of the laying on of hands for those who do not receive communion is inappropriate, even for a priest. Laying on of hands has its own sacramental significance, and to utilize it as a default rite of blessing for those not receiving communion is not appropriate. The document appropriately points out that the proper time for a blessing during Mass is at the blessing after Communion. Under no circumstances should lay people be conferring blessings.