Not sure what the laws are in your state but I will tell you what I know (I am not an attorney).
When you write up your wills…you will appoint someone guardian for your child. This person is the DECISION MAKER and not necessarily the person who will take your child. This is necessary because life changes constantly and you cannot re-do your will all the time to accommodate changes.
Example: My parents are the guardians for my children. If both of us are dead, they will make the decision of what to do with my children. If we die next week, my parents will probably raise them…but if we die 10 years from now, my parents may reconsider what is a better place. Right now my sister is single and may not be the best choice…but what happens 10 years from now if my sister is married and has a happy home and is living out her Catholic faith?
When you pick guardians for your children, these people will be the decision makers and choose what is in the best interest of your children at the time. You may have a family member that comes back to the faith that would be a great choice! Or (sadly) the people that you initially picked may have moved far away or are now divorced. The guardian will evaluate and re-evaluate based on life changes and the ages of your children and what is best at that time.
I know it is hard when you have limited people to choose from. Just pick the best you have for now and let that person know your wishes as life changes. Hope this helps a little.