It is not a good idea either legally (1962-wise) or artistically.

It is sometimes said by well-meaning commentators that Gregorian chant is the ideal setting of its text; nothing could be farther from the mark, for each Gregorian genre shows a distinctly different manner of setting the text—each Gregorian chant is an ideal adaptation of its text to its specific liturgical purpose.

— Dr. William Mahrt, Gregorian Chant as a Paradigm of Sacred Music

Take a look at the striking examples Dr. Mahrt's essay gives for Justus ut palma to see the diverse ways in which the same text may be set depending on different liturgical contexts.

A short responsory is a completely different animal from a communion, thus they are not interchangeable.

In terms of rubrics, look up no. 21 of De Musica Sacra (1958), which concludes by saying that if you can't handle a chant as it is given in the liturgical books, the only options that are allowed are recto tono, or psalm toning. This section also includes a prohibition against altering the text that is to be chanted.

From a certain point of view, one could argue that whether something is Gregorian chant or not depends on context: psalm toned propers are not Gregorian chant; yet the same psalm sung to the same psalm tone is indeed Gregorian chant when it occurs during the office, where the psalm tone is at home.

I agree with Jonathan. A short responsory has another liturgical function than a communion antiphon with psalm verses.

If the antiphon from the Graduale Romanum is too challenging, you could try the simpler melody provided by the Graduale simplex (p. 308).

The Graduale Simplex simply does not pertain to the EF.

True in terms of the law as it stands, but not for the intention of the VII Fathers. They mandated a simpler set of Gregorian chants for use at Mass, and did not mandate the NO as it turned out. And the paradigm of the TLM was, surely, for a chant to meditate on the celebrant's completion of the Holy Sacrifice, not for a large number of the faithful receiving at a sung Mass.

Another thought on GS. It was finalised in April 1965, while work on the NO was only in its first phase. And published, after obstruction from those who did not want official simplified chants, in 1967. That first edition is perfectly suited* to the EF. I acknowledge that PCED probably would not agree, despite their own instruction (my emphasis) :

INSTRUCTION ON THE APPLICATION OF THE APOSTOLIC LETTER
SUMMORUM PONTIFICUM 30 April 2011
28. Furthermore, by virtue of its character of special law, within its own area, the Motu Proprio Summorum Pontificum derogates from those provisions of law, connected with the sacred Rites, promulgated from 1962 onwards and incompatible with the rubrics of the liturgical books in effect in 1962.

[EDIT] * that is in its own terms, to a Missa Cantata where more resources are not obtainable.

Then he cried, but could not hear his own words,

"Flounder, flounder in the sea,
Come I pray thee, here to me;
For my wife, good Ilsabil,
Wills not as I'd have her will."

"Well, what does she want, then?" said the Flounder. "Alas," said he, "she wants to be like unto God." "Go to her, and you will find her back again in the dirty hovel." And there they are living still at this very time.

What the OP needs is a stepping stone, as the specific GR Communion is probably unattainable by children in one jump.

The 1958 requirement that propers, if not sung with polyphony, be sung with the authentic chant from the GR, or on a psalm tone, or recto tono suggests a somewhat unrealistic attitude among the liturgists at the S.C.R. at the time.

This regulation was probably imposed with the intent of pushing choirs to boost their musical skills, to sing not Chants abreges or other simplified chants, but move up to the authentic Gregorian repertoire. I'm not an expert on music pedagogy, but the idea that taking away the training wheels, as it were, would really help singers leap from psalm tones up to the full melismatic repertoire seems implausible to me.

The same attitude of unrealistic recommendations appears in the document's suggestion (para. 25c) that in sung Mass the whole congregation might sing the proper chants; and that this should be undertaken in seminaries and religious communities. Whoever wrote that never heard 30 people try to sing a gradual together. Already the notion that ideally everybody should sing everything (that the choir does not have a distinct role from the congregation) was afoot.