Selling a Lot under tax declaration

Hi Attys and concerned citizens,

I need your help po.

My Lola has a property in Aklan under tax declaration that we want to sell. My Lolo and Lola,both dead had 2 sons.
My Uncle and my Dad.
My Uncle had a wife and they are both dead with no children.
Now my Dad died recently leaving Me, Mom and my 2 siblings.

So we are preparing for all the necessary paperworks.

I already have the following:
-Extrajudicial settlement of estate with publication.(for all of the deceased. Grandparents,Uncle and Dad).
-SPA from my Mom and my 2 sisters. Authorizing me as the executor of all transactions on their behalf.
-NSO docs. Birth,Death and Marriage Certificates.

WHAT ELSE DO I NEED?
I already have a buyer that is willing to give us downpayment so I can have money to pay for all the estate taxes.

I want to be sure if I already have all the documents I need before going to Aklan.

Please help. Thank you in advance.

I'm NOT specialized in property but:

Did your uncle marry after 1987?
If so I believe you need to have documents about your aunt too, because then she got half of your uncle's part by marriage, so then it need to be clearified who inherited that.

And of course you will need the document, which tell you sell the property.

Beside that I believe it's compleete.