@john, treys' reminder was for the first answer to this question.

Answering the main question. No you don't need to acquire an Overseas Employment Certificate (aka Balik Manggagawa Certificate) for your wife and kid. However, to emphasize treysdad's info, if your wife is working here she should be an OWWA member and hence will need an OEC.

May I remind also that the OEC has corresponding benefits. These includes discounts on certain taxes imposed during pre departure back here.