Spain and France

Train would be good but you can fly to Paris from Barca.

Most of the route between Barcelona and Paris is in France, but I suppose it would be possible to loop in a visit to San Sebastian. (I've never been, but it's supposed to be one of the world's great food cities, and a beautiful coastal spot with the Basque culture being markedly different from other regions of Spain.)

You can take a high-speed train from Barcelona to Paris in about 7 hours, so realistically, you’re losing most of a full day just travelling there and back. Is it really worth trying to squeeze Paris into this trip? Honestly, both Barcelona and Paris deserve at least 4 or 5 days each if you actually want to experience something meaningful instead of just collecting train stations.

I’m just wondering what you mean by “nice places along the way.” Since you mentioned you only have 7 days total, how much time are you planning to spend in Barcelona and how much in Paris? If Paris is part of the plan, adding extra stops in between might leave you with very little time in each place.

Just one note on the language side: Barcelona is the capital of Catalonia, where Catalan is the local language. Yet Spanish is also co-official and spoken, especially in the Barcelona metropolitan area, where there has historically been significant immigration from other Spanish-speaking territories, so your mother should have no problem communicating.

That said, the rest of the train journey toward Paris passes only through Catalonia until you reach France, and the everyday language used across most of that area is predominantly Catalan. Even in the south of present-day France, there are some 'departments' (think "counties") where Catalan still has a strong cultural presence alongside French, as that region historically formed part of Catalonia. This isn’t to say you can’t communicate in Spanish, but the most normal thing is that you’ll find people initially, and most of the time, speaking Catalan.

Girona is a lovely small city on the way from Barcelona to Paris. I've enjoyed it on two trips to Spain, but neither was in December.

A bit farther up the rail line is Figueres, which to me isn't an especially interesting place except for the Dali Theatre-Museum, which is a fun stop for people of all ages.

I'm sorry to hear the multi-city option doesn't look affordable for your itinerary, because losing essentially a full day between Barcelona and Paris -- twice -- seems painful. I hate mid-trip flights, though, so I supposed I'd stick with the train if this were my trip.

I don't know where you're starting from to get to Parcelona, but do check again. Usually multi-city flights aren't any more expensive that flights that begin and end from the same place in Europe. Also, when considering, add in your transport time and money. You might find that flying into Barcelona, then post-cruise taking a flight to Paris, then flying home from there, might be more cost-effective. As well as saving you time.

San Sebastian is great, especially for foodies, but would have to get to there from Barcelona, then if you're still planning on Paris, you would have to get from San Sebastian to Paris

I understand the temptation to go visit another country/ major city when you’re already in Europe. That said one of my most important travel learnings is to resist the temptation to do that - particularly if time is limited. There are many great places to visit in Spain if you want to explore around the cruise days that require less travel time than a full day train ride to Paris and then another day back unless you’re looking at an open jaws flight?

I read that one person in the group. - your daughter- wants to go to Paris- what does the rest of the group want to do? If spending two days in transit doesn’t concern you - and train travel can be a lot of fun in itself— then go with the plan!

When I was young a long train trip would be done as an overnight train. Could that be an option for your family?

Your cruise is only a week, not sure what ports you will visit, I assume most. are in the Med, so you may be visiting other ports in Spain, or perhaps France and Italy.

I suggest you consider spending more time in Spain, it reduces you wasted travel time. There is a high speed train to Madrid, spend a few days in that area, visiting amazing Toledo and Segovia on day trips. Also, consider the Prado Museum.

Cordoba and Seville are great visits, as are Granada. If you only have a week or ten days more, the I would recommend the Madrid area and Cordoba and Seville. Seville is very special.