Hmm ... tricky one, Tone. But I'm sure I read somewhere that any *accompanying unmarried children of a Filipino national *who happen to have been born abroad are, in effect, entitled to the same Balikbyan privilege afforded to a foreign married partner, i.e., visa-free entry for a period of up to one year.
IF I am correct and this IS the case, then it should allow Rina & Zayne to travel to the Philippines using the Emirates Airmiles Rewards scheme - thus enabling you to follow through with your original plan of booking their return flights at a later date.