Here are some other possible translations depending on the context:
* Panalangin ng Pagbubukas
* Panalangin sa Pagsisimula
* Panalangin sa Pag-uumpisa
You can also use a more descriptive phrase like:
* Panalangin para sa Pagsisimula ng Ating Pagtitipon (Prayer for the beginning of our gathering)
* Panalangin para sa Pagbubukas ng Ating Programa (Prayer for the opening of our program)
The best translation will depend on the specific situation and the tone you want to convey.