I think you will find that any children born to a Filipina regardless of nationality are considered Filipino under the constitution, you need to check that out, because its a long time since I read it.

My advice is to get your wife to make a will with a professional attorney in the Philippines to the effect that on her death she wishes for the said property to be disposed of in such a way that allows you and your children to remain the sole occupants, you can also arrange to have the property sold to a natural born Filipino in the family for 1 peso on the basis that you are still the sole occupant, that might do the trick.