Is a deed of inheritance sufficient to obtain the inheritance of minor children from their deceased mother, or is a deed of dependency required?

You are the legal guardian of your children according to Islamic law, and you have guardianship over their wealth and their share of their mother's inheritance, without the need for a court ruling. The father is the most deserving of guardianship over a minor, by agreement of the jurists. As for the legal aspect, specialists should be consulted regarding it.