choosing final part of our trip

My general comment is that this is a very fast-paced trip. In 15 days, you have nine different locations where you're spending the night, and a lot of driving. Make sure your group is ok with that. For example, Madrid to a rural finca between Ronda and Sevilla would be at least six hours. And that's not leaving any time to visit Cordoba. I loved Cordoba, and the Mezquita in particular.

While you say that you like adventure, food, and fun, it doesn't seem like you're as much in to history, culture, or art. Which is totally fine, but if you don't care as much about those things, you can cut down on your time in any of the big cities, such as Madrid or Barcelona. And, really, you could skip Cordoba, which is a small city with a huge amount of history. (Though both Madrid and Barcelona are of course are known for great food, in addition to culture and art of various types.)

I live in the mountains here in the U.S., and the Pyrenees might be different, but staying, hiking and/or exploring the Pyrenees in mid-April, there may still be too much snow to do much of that. You should check into that.

You could easily visit Getaria / Zaragosa / Hondarribia from San Sebastian as day trips - we've done that several times. That is, if you want to be in San Sebastian in the evenings. If you want to be in a smaller place, choose one of those other towns.

Enjoy your planning

Perhaps you haven’t driven in Spain before, but Googlemaps estimates are not accurate. Add about 25-30% for the drive time estimated online. And there will be wrong turns at the roundabouts you need to correct for, taking the wrong highway occasionally, highway sign confusion, plus time out for lunch/restroom breaks.

I’m writing this after doing a Spain driving/train trip for 3 weeks which included Madrid/Toledo, Catalonia and Basque Country. I’ve been to Andalusia on a previous trip. You have only two weeks and are ADDING Andalusia/Granada.

You are not giving yourselves much time in the numerous destinations listed. You have one day in Madrid— the day you arrive jet lagged. Only 1.5 days in Barcelona. Each of those cities requires some time to see.

Try to prioritize what you REALLY want to do on your trip and start reducing the number of destinations.
Otherwise, you’re going to be disappointed and exhausted.
In your previous itinerary posted in August, there were 19 days for a similar itinerary. This attempts to condense the timeframe to 15 days with even more destinations added to the list.
I would recommend after Madrid & Toledo, choosing southern Spain ( Andalusia, Antequera, Granada, Barcelona Catalonia). OR northern Spain ( San Sebastián, Hondarribia, Basque Country, Rioja, Getaria)
That gives you 2-3 nights in Madrid/Toledo to recover from jet lag and then 11 nights in the region you choose to concentrate on. That’s all you realistically have time for.

Personally I think you’ve drastically underestimated the amount of travel time you’re going to need as well has how long it will take to visit the places you want to visit. To specifically answer your question, since you don’t have close to enough time to visit the places I enjoyed between La Rioja and Madrid I’ll limit my suggestion to Burgos.

You mention Rioja, but it covers a large area. One could easily spend two weeks visiting that area. Likewise, the Pyrenees covers a huge area. In April you could still come across some very wintry weather in the mountains.

Finally, you intend to go to San Sebastián via Pamplona, but you’ll need to backtrack through that same area to get to Bardenas (where it would be easy to spend a week in that area).

For me the itinerary is all over the place with too many stops to make it a relaxing trip. If you keep the itinerary have a plan B in the event you want to simplify things. Know beforehand what to eliminate if you have to eliminate some things.

This is too much traveling and not enough time to enjoy being in Spain. You’re going to spend most of your time driving and very little time actually doing anything.

Day 15 is not good at all....Zaragoza to La Rioja and then south to Madrid....???

Stop on Day 18 could be Burgos or (my choice) Sepulveda.

But the entire plan seems really rushed.

I'e read mixed reports of Bardenas Reales; you could cut that, maybe.

Day 4--Which "mountain towns??"

You have almost no time in Madrid.

Day 3--do you mean Cordoba is just a quick stop on the drive from Toledo to the "rural fiicna??" Big mistake.
Where is the finca?

There is a lot you ought to rethink here...I agree with others that you are all over the place with too little time to enjoy.

WAY, WAY too many places in 15 days.
You aren't staying enough in most places to enjoy, wasting time traveling.
Spain is a large country and I suggest you reduce your trip to no more than 4 or 5 stays.
Also, you didn't include Segovia, you can do it on a day trip from Madrid.

Suggest skipping the Basque region for this trip. Plan another trip for the Basque region and also take in the Bordeaux region of France, just across the border.

That's a good idea: Skip Basque Spain on this trip and take one in the future that would include the French Pays Basque (maybe Bordeaux if you are interested in wines and food) and the Spanish Pais Vasco. You could also include Rioja on that, later, trip.

From Barcelona, instead of going all the way to SS, you could fly back to Madrid, or take the train with a stop in Zaragoza.

From Barcelona, on Day 9, you can drive to the Emporia for your hiking, therefore staying in Catalunya, and not venturing all the way to the Basque region, which is quite a long way by car.

https://empordaturisme.com/en/blog/the-best-hiking-routes-in-the-alt-emporda/

For me, with 15 days, I would fly to Madrid and stay there, taking day trips (on different days) to Segovia and Toledo.
Then take train to Sevilla, spend 4 nights there, take train to Cordoba, stay a night or two there, then on to Granada...
There are many variations of that--you could include Ronda, Antequera, Jerez, Vejer, Cadiz, Sanlucar, etc. It's a good time of year to be in Andalucia and that region alone deserves two weeks.

If I'm to be honest, I will tell you that your plan is not good; it sounds like a typical first-time-visitor's plan to strike off many places from a. list, without having time to really "see" and enjoy those places.

Besides hiking, what are your interests? Is food of interest? Art museums? History? etc

It really isn't a good idea to fly from Barcelona to Madrid. There are express trains making that run in as little as 2 hr. 37 min.

( Note: The OP’s first post was a week ago and there’s been no post since then).