Q. We recently received the following Shaila from a dear friend of my old country (Mexico) who made Aliya many years ago and sends me occasional yet important Shailos.
As Mazel goes, one of his children’s family settled in the south and a few ended Nebach being captured recently by Hamas, Yimach Shemom, Reshaim. They were saved and released by our Tzahal’s Tzadikim. Yet one child about seven years old could not be found.

Miraculously he was found days later, underneath a big concrete floor plate of a collapsed building. The soldiers saw he was wearing Tzitzis and decided to carry the body to his grieving family. As a soldier picked him up, he incredibly felt a very weak pulse, and yes after likely close to three days, he was still by Hashem’s miracle alive! (He asked me not to mention his name, as they stick to privacy.)

A. Of course, the family got together to perform a private Seudas Hoda’ah as required. His Shaila was, does the kid have to bench Goimel or do the parents bench for him?

Horav Shlomo Miller’s Shlit’a opinion is that reciting the Goimel bracha is not recited. The reason is that the text of the bracha is Hagomel l’chayavim Tovos,” and since a child is not a chayav or guilty yet, children don’t recite this bracha, and hence neither do the parents.
Yet, as you mentioned a Seudas Hoda’ah should be served to publicly express thanks to Hashem for the miracle Hashem did for you (See Magen Avrohom 219: 1). Yet some Poskim maintain that a minor does recite Hagomel.(Shaarei Teshuva 219: 1, Lachamei Todah, and others.)
The main principle is there, we recite thanks to Hashem when we truly understand the gift of life and salvation given.