I haven't been to Italy/Switzerland BUT just returned from a trip with DM (68) and DD (18). We were on the Danube River Cruise and it worked very well for a multigenerational trip. There were about 8 to10 groups of grandparents, parents, and children cruising and it was a wonderful trip.
That said, I've heard great things about the Italy/Switzerland trip as well!
One thing to consider is the cruise ship's ac works very well, unlike some of the more historic hotels in Italy/Switzerland. This was quite important to us since there was a heat wave in Europe while we were there.
Truly, I don't think you can go wrong with any of the itineraries but depending on your mother's level of fitness, river cruises can be slightly more relaxing. My mother isn't in the best of health so that was a large consideration in the trip we chose.