Let me lead you to the highest summit of Germany by foot from Garmisch-Patenkirchen an ascent of 21 kilometers with 2300 meters hight difference - an easy hike I personally did together with my two sons aged 8 an 12 at the time.
Listen to the sparkling sound of the waters, the sweet singing of the birds in the trees and the howling winds along the heights just to enter the social huts with accomodation, food and drinks of the infamous Bavarian culture of hospitality.
WARNING:
This trip is a serious alpine trecking trip - you should be experienced in the moountains and climbing, mentally and physically fit, well equipped with supplies and gear for al weather conditions and check the weather app and have some money and all your senses with you.