We researched different sources and recommendations for dietary needs and the amount of water that should be stored in order to have enough calories for a sustained physical activity level (PAL) of 1.8.
Kids from 0-10 years: 90kcal/kg body weight, 50ml of water/kg
Youth form 11-18 years: 90kcal/kg body weight, 40ml of water/kg
Adults (18+): 45cal/kg body weight, 30ml of water/kg
Recommended ratio of calories: 28% fats, 60% carbo-hydrates, 12% of protein.
You can adjust your calculation to your PAL, for sustained sitting out of a crisis, we assumed a PAL of 1.2.
Sources
http://www.bmi-kind.de/kalorienbedarf-kinder/
D-A-CH Referenzwerte für die Nährstoffzufuhr, 2. Auflage, 2. aktualisierte Ausgabe 2016
www.ernaehrung.de/tipps/allgemeine_infos/ernaehr10.php