Hi Stella,
I am Andy, I am also going on this trip on the 7th of August and this will be my second time on this trip, As I was there last May. All the trips are very well worth going on to be fair and they are all very intersting. There are already 2 included excursion to Salzburg and Hallstatt, Aswell an evening lake cruise, which are very Intersting places to go on, But the optional trips, I can reccommend them all really. So I guess it is up to you. What I think I perhaps should say, Is that even on some of the excursion, There are other things that can be done, Like visit the salt mines in Hallstatt and possible a lake cruise there too. To be honest I like them all really as they are all different and I guess it is really depends on your budget etc. What I will say, It will be a busy week.
I would be happy to discuss with you in more detail once at the location.
See you in about 12 days
Regards Andy