Here is some information about the Order for the Blessing of an Engaged Couple in the Roman Catholic liturgical book “Book of Blessings”. Perhaps it will be helpful in making your decision.
The numbering is from the USA edition. The blessing is in the original Latin book. It is not one that has been added for the USA.
The introduction to it includes:
“196 When the engagement is celebrated within the circle of the two families, one of the parents should preside. But when a priest or deacon is present, the office of presiding more fittingly belongs to him (provided it is clear to all that the blessing is not the celebration of the sacrament of marriage itself).
197 The present order may be used by the parents, a priest, a deacon or a lay minister. While maintaining the structure and chief elements of the rite, the minister should adapt the celebration to the circumstances of the place and the people involved.
198 The present order may also be celebrated during the engagement period on an occasion when couples are brought together for premarital instruction. Neither a formal betrothal nor the special blessing of an engaged couple is ever to be combined with the celebration of Mass.”
Here is an outline of the ceremony. It begins with the minister saying “In the name of the Father, and of the Son, and of the Holy Spirit.” All make the Sign of the Cross and reply “Amen.” There is a greeting and introductory words from the minister. There is a reading from the bible by the minister or one of those present. There is a responsorial psalm or “some other suitable song.” The minister may given a brief explanation of the biblical text. Next are the intercessions, introduced by the minister, read by an “assisting minister”. The next part of the intercessions is:
“ 209 In accord with local custom, before the prayer of blessing, the engaged couple may express some sign of their pledge to each other, for example, by signing a document or by exchanging rings or gifts.
210 The engagement rings or gifts may be blessed by use of the following formulary.
In due course may you honor the sacred pledge
symbolized by these gifts which you now exchange.
R. Amen. ”
The next heading is “Prayer of Blessing”. The are two, one for only Priests or Deacons. This is the one by a lay minister or ordained minister:
“ We praise you, Lord,
for your gentle plan draws together your children, N. and N. ,
in love for one another.
Strengthen their hearts,
so that they will keep faith with each other,
please you in all things,
and so come to the happiness of celebrating the sacrament of their marriage.
We ask this through Christ our Lord.
“213 The minister concludes the rite by saying:
May the God of love and peace
abide in you, guide your steps,
and confirm your hearts in his love,
now and for ever.
214 It is preferable to end the celebration with a suitable song.”
[Excerpts from the English translation of Book of Blessings, © 1987 International Commission on English in the Liturgy Corporation. All rights reserved.]