This is a question for optional excursions in general. How do they work? Does the bus drop you off and pick you up from the places you pick or do you have to find your own way around? Is there time to do more then one or do you have to pick only one per day?

You generally get a list of optionals (and their costs) at the start of your trip. You pick the ones you want at that time and pay for them soon after.

There can be 1-2 optionals per day (city/monument/special tour and dinner). Some days there are none (travel days).

For most optionals the bus will drop you off and pick you back up (especially for optional dinners). Depending on what the optional is (ie: if it is a city/special place tour) the bus may come back to get you but you don't have to go back with it if you don't want to. If you want to stay and explore the area you are in more you can BUT you then have to get your own way back to the hotel (which is sometimes a fair way out of the city).

If you know which trip you want to do have a read of the itinerary and a look at the optionals listed for it - it will give you a better idea of what's offered when.