We have been on many river cruises in Europe but not Viking. The Viking trip we are doing in May is on the Great Lakes and my concern was the flight, but they will meet us at airport. When we went to Amsterdam pre-dementia, the city was pretty easy to get around and walk, although it was a good bit of walking so you might want to consider taking a city tour bus or just look at brochure highlights and map to decide what he could handle before getting too tired. We didn’t use Uber but that could be a help to have the app just in case and of course have the address where you are staying in writing on you and your husband at all times for id. Also make sure his wallet has your phone number, just in case. River cruise people are very helpful and gather guests like baby ducks very well. Pre-dementia we would drift away from the tours because we were adventurous but I would not advise that now. I think we just took a cab from the airport to the ship when went so that should work for getting to the apartment. Make sure you have maps and/or navigation on your phone! I will fill you in when we return, fingers crossed.