I will start by saying that we did most everything everyone suggested and they are all just like they said...beautiful, beautiful, beautiful. So I will tell you a couple of things that we experienced that most have not said.
We did two things in Vienna that were the "highlights" of our 3 week trip.
First was the High Mass at the Imperial Palace with the Vienna Boys Choir and the philharmonic (part of them anyway). My husband was not excited about going to a high mass (in Latin) and all sung by priests that probably should not sing...well more like chanting...but....it was almost unreal. They tuck the boys and the musicians up in the upper loft (I think). Wherever they are, you cannot see them, but you can hear them. It was the most intimate setting and heavenly music. The music was Mozart's last gospel music he had written and the philharmonic was incredible. If you reserve your seats early you can get fantastic seats - we were in row 1. You can only reserve and not pay until the day of the mass. They do not take credit cards so come with cash. It is not expensive! You can pick up the tickets 30 minutes before the mass starts or the day before if you happen to be in the palace area. After the mass the boys come down and sing one last song for the audience and you are allowed pictures at this time. They were so cute and even though they perform all the time they actually looked embarrassed by all the attention. My husband, who didn't want to go, said that was "the best venue" he has ever been to.
The second thing I will tell you about is that we did the trip to the Wachau Valley with the fantastic help of the TA experts. It works like clockwork just like they tell you. One thing - when you go to the train station at 06:15 there are very few people to ask where to buy the tickets. It is on the level just below the platforms on the back wall. Not really marked to stand out. We had a bit of a problem finding it but finally asked a EOBB train person and were able to get there in time. We bought the Combi tickets - train tickets, Abbey voucher and boat voucher. We took the 06:50 train to Melk. Arrived there at 08:04. We walked around a bit on the way up to the Abbey. Got to the Abbey around 08:35 and knew that we had to exchange our voucher for a ticket. As we walked through the courtyard there were already several LARGE groups waiting to get in. They do not open until 09:00. We exchanged our voucher and they told us we could go on in and get started (since we were individuals). We were shocked as this meant we were the first ones in, before the opening time, before the groups, and we had the Abbey all to ourselves! It was fantastic! Can you imagine going through everything (it is all in English) including the library and cathedral with NO ONE there except you? Maybe it is just because we are not a big crowd people but it just made the day all that more special.
After we did the Abbey we got a cup of coffee at one of the quaint cafes and relaxed for about 20 minutes and wandered on down to the boat dock, doing some shopping along the way. Got to the boat dock and again exchanged our vouchers for tickets and got on the boat. It was a beautiful sunny day. Not too hot, just right. We had a nice glass of wine while sailing down the Danube. We got off at Durnstein and had lunch, did some more shopping, and found the bus stop to ride the short ride to Krems. We did have to ask directions to get to the right stop (we were on the wrong side of the street). Got to Krems around 15:00 and wandered the streets a bit. Had a wonderful ice cream sundae and then took the train back to Vienna in time to freshen up and go to the Musikverian for that nights concert.
We were afraid that all of this might be too much for semi-old people like us, but it was just perfect. Loved Vienna and the people that live there.