We will be taking the Rick Steve's Portugal tour in October and are looking for recommendations for day and/or overnight Douro wine cruises that we could take after the tour ends in Porto. Thank you for your help.
Several companies offer overnight Cruise into the Douro Valley.
Usually it's upriver on the boat, overnight at hotel, visit vineyard and return by either train or bus.
https://www.cruzeiros-douro.pt/en/2-days-cruises
https://www.roteirododouro.com/en/douro-cruises/2-day-cruises
You might want to consider the weather and state of the vineyards when planning. It rains a lot in the north and depending on the week you’ll be there, peak vineyard season might well be over. However many quintas are open, so at least there will be tasting.