3GenMemories

I was planning to fly from Barcelona to Zurich/Basel and take the train to Wengen. We're okay backtracking a bit in the drive if that's what is needed.
My kids are 3 and 6 years old. They are used to walking 3-5 miles a day and love hiking, biking, skating, skiing, swimming and watching people.

The overall plan was to run around the city (Barcelona), then have a laid back countryside/beach vacation (France) followed up hiking in the mountains (Switzerland). I'm hoping to strike a balance so kids and my parents don't tire down too much.

kja

I trust you realize that you can have a "laid back countryside/beach vacation" on the Costa Brava. No need to venture into France unless you want to.

For that matter -- and I'm just throwing this out as an idea -- you can also experience the beaches of San Sebastian and thereabouts and you can hike in the Pyrenees and the Picos de Europa, so no reason to go to Switzerland, either (although it is magnificent). You can meet ALL of your interests just in northern Spain and Catalunya!

Here's another of my trip reports that covers Barcelona and those parts of Spain:
Four Awesome Weeks in the North of Spain and Catalunya

jpie

IMO you might be best to choose between the beach areas of Spain and France since driving from Barcelona and dropping a car in France will be expensive and I think the laid back beach vacation part you can get would be somewhat similar in either country in a way.

What about the idea of spending the first portion in Barcelona and then picking up the car there and driving to Roses (or somewhere around there for the beach part), and then dropping the car in Figueres, and then taking the train to Toulouse, which is a great city for families, lots of fun stuff for kids and nice restaurants and sights for adults as well. From Toulouse you can either fly to Zurich (1 stop connecting) or non-stop to Geneva and take the train from there which is a nice ride. Toulouse is one of the nicest cities in France IMO and that would give you a nice opportunity for the French break your son wants and you wouldn't have to backtrack to Barcelona.

jpie

Another thought would be to skip France completely and to fly from Barcelona to Geneva and spend a few days in the francophone part of Switzerland then take a train up to Wengen from there.