Information can be found in the brochure My child is disabled - these aids are available http://bvkm.de/wp-content/uploads/2016_Mein-Kind-ist-behindert-diese-Hilfen-gibt-es.pdf
Children and adolescents who are physically or mentally handicapped or who are threatened with such disability may receive benefits from the integration assistance https://www.elternimnetz.de/kinder/sorgenkinder/hilfen.php#5
Help provide the social and youth welfare offices.
An overview of organizations and foundations that support seriously ill and disabled children and their families is given here: https://www.myhandicap.de/recht-behinderung/finanziellen-hilfe/kinder-jugendliche/