Translated from Ustadz Firanda Andirja's Indonesian commentary (Bekal Islam). Quoted verses, hadith and duas keep their Arabic; where the commentary gave its own Indonesian rendering of them, that rendering is not translated and is marked [translation not shown].
The dua of the Prophet (peace and blessings be upon him) above uses the second-person pronoun for two people (kumaa), because those the Prophet was praying for were Hasan and Husain.
If the one being prayed for is a single boy, then (kumaa) is replaced with (ka), so that the wording is as follows:
أُعِيْذُكَ بِكَلِمَاتِ اللَّهِ التَّامَّةِ، مِنْ كُلِّ شَيْطَانٍ وَهَامَّةٍ، وَمِنْ كُلِّ عَيْنٍ لَامَّةٍ
"U'iidzuka bikalimaatillaahit-taammah, min kulli syaithoonin wa haammah, wa min kulli 'ainin laammah."
As for a girl, the wording is changed to (ki):
أُعِيْذُكِ بِكَلِمَاتِ اللَّهِ التَّامَّةِ، مِنْ كُلِّ شَيْطَانٍ وَهَامَّةٍ، وَمِنْ كُلِّ عَيْنٍ لَامَّةٍ
"U'iidzuki bikalimaatillaahit-taammah, min kulli syaithoonin wa haammah, wa min kulli 'ainin laammah."
If there are many children, it is replaced with (kum): أُعِيْذُكُمْ