My daughter wants me to take her children and raise them. They are 4 and 2. Both she and the children's father (they are not married) feel they are emotionally and mentally unable to care for them properly. I live in Florida and they live in Massachusetts. What are the legal ramifications of my taking the children to live with me and do I need to go to court for this (and in what state) or will a notarized letter of temporary custody be enough for me to be able to enroll them in school and get medical treatment for them if needed? Any and all advice is appreciated as my daughter wants me to come get them immediately and I am worried about her mental health.

I would suggest that the parents sing an order of temporary guardianship to you and file that with their local Family court. This should be enough for you to register them in school and get medical care.

Once they have resided in FL for 6 months, you can then file for legal custody.