Protecting a Minor (Last Will)?

I have a 2 year old child. I have some real estate personal properties.My son's father is an American. My mother and siblings live with me. My concern is in case that something happens to me, how can I be sure that my family who don't have jobs will not sell my properties? I want my child to inherit most of what I have but he is too little to know. He would be able to use it in the future for his education, etcetera. If I make a will how can I be sure that they would obey what is in the will? Can I appoint the American as my executor, but if I do so, how can I be sure that he will not also sell the properties?