Hello and welcome to you both.
I have in the past brought my ex-wife's 2 children from the Phils to the UK.(then aged 7 and 9 years).
They are both at university here now.
No need for adoption.
Yours will come as dependants of the wife.
You will certainly need their birth certificates on NSO paper, and I would anticipate, the father's death certificate.
As it was some years since I went through the process, I would suggest you do some research on the UKBA site to get the most up to date information.
PS...don't forget to get them passports !
