Choose a transport option - car, flight, train - and the nearest airport or major station. For Bavaria and Austria, the obvious ones are Munich and Salzburg. The less obvious airports are Memmingham, Ljubliana. Linz.
Pick a resort or two. E.g. Saalbach, Zell am See.
See if the Tourist Office has a website with an accommodation service.
Also look at Booking.com, vrbo, airbnb. For hotels, look at the reviews on Tripadvisor.
For specific questions - e.g. does anyone know Hotel XXX in NNN - ask again on here.
Alternatively, the usual tour operators ( Crystal, Inghams, TUI etc) have "Lakes and Mountains" programmes for the summer which might give you some ideas.