We are going in April. It happens to be Easter when we arrive so I am not sure if the tours will be different. The 3 optional excursions they are offering us are an Art and Architecture tour, Wine and lunch in Eytek and visiting a horse ranch Pustza. They are only offering one included guided sightseeing tour.
We will be there 3 days/2 nights at the start of our trip and it is Easter Sunday and Monday so we are not looking to book too much as I read there is a festival that coincides with Easter and they have markets similar to Christmas markets. But we did sign up for the wine tasting tour.
I too am interested in hearing from people who have done both included and optional excursions with Avalon. This is our first time on a river cruise. I think I expected a lot more activity than what they have offered in the included tours and I think so far have added about $750 in optional excursions. They do a good job on the details when they show you the optional tours. Be sure to also look at what the travel time is. One we are doing has 4 hrs of travel.