As Adiyen had performed Bharanyasam, adiyen did not worship demi-gods; before bharanyasam adiyen had celebrated Vinayakachaturti, as it was a festival celebrated from my childhood days; my parents who had performed bharanyasam insisted on celebrating it even now saying one can consider it as a celebration for Vishvaksenar; adiyen had explained to my ability that they are not the same; but they insist Vinyakachaturti can be celebrated if you have children at home. Moreover, an astrologer had told my mother some 50 years ago to worship Pillaiyar due to the malefic effects of Ketu on her son and since then she has been celebrating for the past 50 years despite her bharanyasam. After her bharanyasam she has been regularly reciting Paduka Sahasram, Desika Prabandham, and Acarya thanian every day sincerely for the past 15 years. My father is 92 years old and has been performing daily austerities and Tiruvaradhanam every day. Don’t know why the attraction to demi-gods. Adiyen is clueless as to how to make them understand, please advise.

You can make them understand by quoting some more references that Vishavaksenar and Pillayar are not the same. While Vishvaksenar belongs to our Acarya goshti, he is Perumal’s Chief-of-Army and one of his army personnel is Pillaiyar; Vishavaksenar has two tusks along with conch and discus, unlike Pillaiyar who is one tusked minus the conch and discus. Those who have performed Bharanyasam should not worship demi-gods.
No harm will occur if we do not worship any demigods. Azhwar sang ‘nAvaliTTu uzhitaruginROm naman-tamar talaigaL meedhE’. As these demi-gods are under Emperuman, they shall never cause harm to His devotees. A sharanagata should have absolute faith.
If one has a fear of Ketu dosham, Garuda Panchashat can be recited as a remedy as it annihilates all the sarpa dosham. As you have mentioned all the Desika stotrams can be recited. To mitigate one from this fear reciting Garuda Panchashat will be effective.
It is not harmful to have celebrated Vinyakachaturti before bharanyasam, as bharanyasam would have eradicated the sins that have been accrued before; but after bharanyasam when we knowingly commit, it shall become a sin; the thought of the youngsters will prevent the elders from committing such offense.
To make them realize, they can listen to the kalakshepam on Shrimad Rahasyatrayasaram delivered by Sri U Ve Navalpakkam Vasudevacharyar on the link provided https://www.sampradayamanjari.org/kalakshepams/.