My philippine wife and our 2 american born children are going to philippines on balik bayan privilege program. She is natural mother of children. Just to be on the safe side I will get a outbound ticket out of the philippines,just in case airlines require it. My question is do the children also need outbond ticket being they hold american passport? Keep in mind their natural mother is a philippine citizen.

... do the children also need outbond ticket ...?

Correct: the airline won't let the children on the plane for their return journey unless they have tickets. This is of course obvious, so perhaps I misunderstand your question.

The children are Philippine citizens, so it would be easier for them to enter and exit the Philippines on Philippine passports.

There are no restrictions for US citizens entering the Philippines as tourist as long as they are staying for under 30 days, have a valid US passport, and can present a return ticket or a ticket for transport onto another country. If your family intends to stay for over 30 days, they can apply for a visa extension for an additional 29 days. Beyond that you will need to look into obtaining visas before travelling.