75 year olds begin in Amsterdam and want to see Lake Como - 17 days - please help!

Why did they book a ticket to Amsterdam when they want to go to two towns Italy and when is the flight? You can fly to Milan or Naples from Amsterdam maybe start there.

What river & from where to where? HOw are they going to travel on land?

Michelin Green Guides are the key to planning because they have a compact map locating all the worthwhile sights by quality rating
Change airports if possible to Munich or Frankfurt (don't stop in either city).

You pose the most challenging itinerary question I've ever seen--"not have them moving every two days and appreciates the fact that they prefer smaller, quaint towns to massive cities". This can be done but only best by car-- train-bus is just to infrequent to be efficient. While there are quint small towns all over the place, finding a concentration of them where you can stay for more than 2 days is the challenge. Here are the possibilities: 1] Route de Vin Alsace, Route de Cretes, and Black Forest, France. I'd stay in Kaysersburg; 2] German Romantic Road stay central, like Nordlingen; 3] Salzkammergut I'd stay in Bad Ischl , Austria (Small places + mountain scenery); 4] The Middle Rhine & Mosel Valleys (just north of Alsace, St Goar, Boppard, or Koblenz). You need a loop to go AMS/AMS: Rhine, Alsace, L. Como, Romantic Road.

What time of year is the trip?

The flights are booked? If not, an open jaw/multi-city ticket may be better than a r/t through Amsterdam

If the flights are not booked yet, definitely look at an open-jaw ticket.
I suggest choosing between lake Como or Sorrento if they don't like to travel too much. And if you are based in Amsterdam or its surroundings, it's easy to make day trips from there. Even Belgium is literally just around the corner. Travelling by train will be the best option in that area of the world in my opinion.

A possible route could be: Amsterdam - Würzburg - Verona - Como - Milan.
Amsterdam to Würzburg has a perfect rail connection: 5h30 with only one change of trains. Würzburg will keep your parents busy for a day and it is a good base for day trips, such as Bamberg or nearby Ochsenfurt and Marktbreit.
The train from Würzburg to Verona is a long day on the train (8 hrs or more), but goes right through the very scenic Dolomites mountain range and can be done with only one change of trains.
I have no experience with the Como region, but Verona has at least good rail connections with the city of Como.
Flying back home from Milan is the obvious choice with such a itinerary.

There was some good advice in responses to your previous post https://community.ricksteves.com/travel-forum/italy/76-year-old-parents-italy-help-for-them. Flying to Naples from AMS seems to make a lot of sense,

They could always travel by train along the Rhine River to Cologne, Koblenz toward Munich. Then down into Austria and Northern Italy going toward Lake Como north of Milan. Then catch EasyJet out of Milan back to Amsterdam Schiphol airport on an inexpensive flight.

Thanks for the replies. To answer some of your questions... they are flying from PDX to AMS in mid April next spring. Why? I DO NOT KNOW! My Dad "likes" this direct flight, times, prices, etc... so he went ahead and booked it. It's very illogical to me considering the places they wanted to go, and that's why I'm trying to help them. They had planned to fly from AMS to Naples, but I am trying to get them not do that as that makes the travel day so incredibly long and stressful for them. (My dad is a very nervous traveler.) The flight my Dad found from AMS to Napoli is about 5 hours after arrival and then they still have to get from Naples to Sorrento. Here's the deal, my parents aren't in the best health and as their concerned daughter, I think that travel day is just too much. Hence, my wanting to go a different, yet just as enjoyable route for them. I've convinced my Dad that Amsterdam is worth seeing and spending some time at, allowing their bodies to adjust to the time and having that initial day be less stressful for them.

Since they have not seen Lake Como and it seems to be on their bucket list, I'm trying to create an itinerary that gets them there. They are NOT opposed to taking an additional flight somewhere during their travels. I just wanted to avoid it on that initial arrival day, if possible.

If you are able to convince them of the wisdom of spending a 'few' days in Amsterdam before going on with a flight to Naples to fulfill their desire for Sorrento, then go to Lake Como and then fly Milan to Amsterdam at least the day before their return flight home.
With this plan they have 3 days that are mostly devoted to travel so trying to add in other destinations seems unnecessary and gives them time to enjoy Sorrento and Lake Como at a relaxed pace and not put undue stress on them. If they need an additional stop ,would Lucca work for them as a between Sorrento and Lake Como location?