The liturgical books have no description of this practice of blessing during the distribution of Communion. I suggest remaining in your seat.
There are official blessings described in the RCIA book. Stick to these, rather than an unofficial one, likely to cause confusion about whether you are already receiving Communion, since you are in the Communion Procession. From the RCIA liturgical book:
“40 During the precatechumenate period, parish priests (pastors) should help those taking part in it with prayers suited to them, for example, by celebrating for their spiritual well-being the prayers of exorcism and the blessings given in the ritual (nos. 94, 97).”
“47. … The catechumens should be eager, then, to take part in celebrations of the word of God and to receive blessings and other sacramentals.”
“BLESSINGS OF THE CATECHUMENS
95 The blessings of the catechumens are a sign of God’s love and of the Church’s tender care. They are bestowed on the catechumens so that, even though they do not as yet have the grace of the sacraments, they may still receive from the Church courage, joy, and peace as they proceed along the difficult journey they have begun.
96 The blessings may be given by a priest, a deacon, or a qualified catechist appointed by the bishop (see no. 16). The blessings are usually given at the end of a celebration of the word; they may also be given at the end of a meeting for catechesis. When there is some special need, the blessings may be given privately to individual catechumens.”
The RCIA book encourages catechumens to not even attend the second half of the Mass, the Liturgy of the Eucharist.
“75. … 3. The Church, like a mother, helps the catechumens on their journey by means of suitable liturgical rites, which purify the catechumens little by little and strengthen them with God’s blessing. Celebrations of the word of God are arranged for their benefit, and at Mass they may also take part with the faithful in the liturgy of the word, thus better preparing themselves for their eventual participation in the liturgy of the eucharist.
Ordinarily, however, when they are present in the assembly of the faithful they should be kindly dismissed before the liturgy of the eucharist begins (unless their dismissal would present practical or pastoral problems). For they must await their baptism, which will join them to God’s priestly people and empower them to participate in Christ’s new worship.”
So in a sense it is better not to be there for the Liturgy of the Eucharist (never mind joining the Communion Procession).
The extracts above from the RCIA book is from the edition for England and Wales at
catholic-ew.org.uk/liturgy/Resources/Rites/RiteRitual.html#RCIA . The USA edition has some different paragraph numbers.