participle phrase or to-infinitive phrase

In response to the long-term measures recommended by the School Board,
the then Principal initiated the Pledge Day on “Clean LA", to encourage
all schools to make the “Clean LA” commitment on that day.

I wonder if it sounds better to replace the to-infinitive clause with a participle clause:

In response to the long-term measures recommended by the School Board,
the then Principal initiated the Pledge Day on “Clean LA", encouraging
all schools to make the “Clean LA” commitment on that day.

because I think it is seldom to use to-infinitive clauses after a comma.

Answer

"To encourage" and "encouraging" both sound fine to me. There's a subtle difference:

the Principal initiated the Pledge Day, to encourage ....

This answers the question, Why did the principal initiate the Pledge Day?

the Principal initiated the Pledge Day, encouraging ....

This means that through initiating the Pledge Day, the principal was, in this way, encouraging....

(Note, the comma is fine.)

There's a third option:

the Principal initiated the Pledge Day, and encouraged ....

This one suggests that perhaps the principal held an all-school assembly, where he explained the concepts and provided encouragement.