Can my Ex-husband's IRS debts hurt my children or they inheritance?

My Ex-husband has a major drug problem and has not filed taxes since I left him in 2004. He has had a large amount of income since (the amount is unclear) which he has blown. He is a 1/3 owner in a partnership with his brother and mother which includes property of 500 acres that has been in the family for five generations. I know I had to have a Will when I was married to him to to obtain the property or it would go to the right to survivorship of the other parties upon his death. I do not want my children to inherit his tax obligations, but I do not know how to prevent it. He is homeless and broke now and he is nearing death of the drugs he loved so well. I know if my daughter is the executor of a will she will be responsible. I don't think my kids should have to pay for the fathers mistakes. Please help!!!