I live near Braunlage in the harz region. I speak horrible german and have less language problems here than i had in Berlin. Housing is reasonable but these are small towns, so not sure how any special needs for your son would be such as in school. There are lakes all around but not sure about swimming as most are for drinking water. Lots of waldbads. There are 100s of kilometers of hiking and biking trails. Cross country skiing and small downhill areas also. There were spruce trees as far as you could see but not now...all clear cut for the bark beetle. But still nice and lots of nature. Houses in smaller villages that are liveable but may need minor freshening for a little over 200k can be found with land but you need to search. Some nice homes pop up in walkenreid and weida from time to time. Braunlage proper is not cheap. Many decent homes in and around the small towns in harz. But it snows quite a bit and winter can be long at the upper elevation towns. For money you cant beat it if you like small and quiet. People are friendly and you do need a car here.