This is the 11814th most frequent Spanish word.
haciéndolos
"Doing them" or "making them."
The word 'haciéndolos' is used here to describe the action of creating a welcoming feeling for 'them'.
Estoy haciéndolos sentir bienvenidos.
I am making them feel welcome.
Here 'haciéndolos' expresses an ongoing action that results in the happiness of 'them'.
Por favor, sigue escribiendo esas cartas, haciéndolos felices.
Please keep writing those letters, making them happy.
In this sentence, 'haciéndolos' is used to indicate the transformation of their mistakes into correct answers.