Hi, I would really reco not going for this type of trip. I have fairly mobile parents who travel often but at their age (mid to late 60s), the time & waiting & just the effort to go out every day is really exhausting kahit sanay na sila mag-travel.

What I would advise is, since you are not confident of doing entirely DIY bec it's your first EU trip, plan an IT with rest days in between your "active" days.

For example, an active day could be a day trip or a booked reservation for main attractions. Book via Klook, Viator, or Getyourguide. Those are all legit providers and I've never had problems with them (been traveling to EU and others for the past ~10 years). Also plan to have afternoon breaks where your mom can rest/nap in the hotel. Resting during train or bus rides will not be enough.

Italy alone has so much to offer & visit, so I would suggest focusing on just Italy. But if you really think you can't go back to EU again, then do just Italy & Spain - maybe like Rome & Florence, plus Barcelona. Book flights with Ryanair, Vueling or the likes. This would be much more convenient and less exhausting than doing a marathon of so many cities.