My question involves a child custody case from the State of: Arizona and Colorado

I am the mother of a 9 year old child. I have been in a committed relationship for 6 years and married to that man for 5 years. My child's biological father lives in another state (CO) and has seen the child a total of 14 days since the child's 2nd birthday. He is current on his child support and calls occassionally...maybe once per month for less than 5 minutes. He is allowed supervised visitation (due to domestic violence/drug issues) as of now, but has not visited the child in 4+ years. He refuses to voluntarily terminate his rights. My husband is the only person this child has in its life as a stable, loving parent. I have been diagnosed with a terminal illness and am attempting to "get my affairs in order". Is there anything I can do to help assure that my husband/step parent will assume legal/sole custody of my child after I die?