The children, aged between 4 and 5, belonging to the Sacred Heart church at Kumbalangi near Kochi, handed over the hand written letters in Hindi, English and Malayalam to Ernakulam MP, Prof K V Thomas, who were present at the function.
The children were helped by their parents and church priests in writing the letters, church sources said.
Thomas said he would be handing over the letters to Prime Minister as early as possible.
Parish priest and 20 others members are also coming to Delhi and we will try to meet the Prime Minister on Wednesday or Friday, he said.
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Earlier, special prayers and candle light vigils had been held in various parts of Kerala for the release of the 55-year-old Salesian priest, Fr Tom Uzhunnalil, who was abducted in March 2016.
The priest, who was abducted when IS fighters stormed the Old People's Home in the port city of Aden on March 4, had made an emotive video plea to the Indian President, Prime Minister as well as Pope Francis and the Christian community across the globe to work together for his release.
"I am a priest from India and perhaps, therefore, I am not considered of much value. I am sad about this," he had said haltingly, pointing out that a French woman, reportedly kidnapped in the Yemeni city of Sanana, had been freed.