My eldest son also has dual nationality (UK/Phil) Born in England. I procured 'Recognition' (as a Filipino Citizen) status and certificate for him, from the BI in Manila, back when he was 2 years old.

It has his (baby ...lol) photo, and more importantly, his thumb print, on the certificate.

He could use this to apply for a Philippines passport, if he wanted one.

It also means he can reside in the Phils with all the rights of any other Citizen (and visa-free).