My very dear one,
I am very sorry it took a long time to reply.
According to my observation it comes out best for your son to recite Lama Tsongkhapa mantra (migme mantra) every day. The best would be four malas a day, if not then at least one mala a day, with meditation.
Then, request the geshe to perform ga gön puja. Geshe-la will do the meditation and short ritual for your son.
Regarding the Lama Tsongkhapa practice, you can ask Geshe-la to explain a little how to do this meditation. If possible, your son should visualize Lama Tsongkhapa while reciting the mantra. Beams of nectar emit from Lama Tsongkhapa and his two sons and the beams all become one beam. This enters his crown and blesses his body, speech, and mind. Think that it purifies all his negative karma, defilements, spirit harm, and sickness collected since beginningless rebirth.
The other thing that came out very beneficial is for your son to receive Rahula initiation. This initiation is mainly for paralysis, but it comes out very beneficial for your son. After he receives the initiation then he should do the torma offering practice and meditation. It may take some time for him to receive this initiation, so for now start with the two other things I’ve mentioned.
I am also making prayers for your son, and also the Sangha in my house are dedicating animal liberations and the making of long-life tsa tsas to him.
With much love and prayers...