How should the three children, under the age of four, enter into a state of ihram, how do they perform the rituals, and is it better for them to shave their heads or shorten their hair for exiting ihram?

The Hajj and Umrah of a discerning child and a non-discerning child are valid by scholarly consensus. The Umrah of a non-discerning child is performed by their guardian intending the ihram on their behalf after dressing them in ihram garments and keeping them away from prohibitions, then intending the circumambulation (tawaf) and the ritual running (sa'i) for them. It is preferable to carry the child during the tawaf and sa'i, and one circumambulation is sufficient for both the carrier and the carried. After that, the child's hair is either shaved or shortened; shaving is preferred, but if there is a reason necessitating shortening, such as fear of cold, then there is no harm. If the child commits a prohibited act out of ignorance, there is no fidyah (expiation). If it is done intentionally, the fidyah is upon their guardian.