Issues that may arise in minor property

I'm writing on behalf of my sister who is heading for a divorce , as her husband is not at all taking care of her and her 7 year old son. Her husband was working as welder abroad at the time of their marriage but later returned.Since then, we found him to be totally irresponsible in family matters.He is a drunkard and he sold off all of my sister's jewellery (which my parents gifted her at the time of her marriage) towards the same purpose.He is never available for them either physically or in financial needs.He was given plenty of chances to change, but in vain.My sister and son now lives with us in our parent's home.We don't find any meaning in taking this relation forward as loving and caring has been a one way thing throughout this relationship. He has only a property left in his name ( of which a part is ancestral and the remaining was purchased from his sister years ago , selling a part of my sister's jewellery).We had asked him to give that property in my sister's name towards the damages incurred.But he isn't ready to do that.Instead he says that he is willing to give it in their son's name.(Please note that he is a minor and just 7 years old.).Meanwhile we have found out that this person has plans to pawn this property too. Will it be safe making him the guadian of this minor child's property? ( We dont think that he would ever agree to keep my sister as guardian). Is there any better options available?