7 days in Seville and Andalusia region of Spain-late summer 2026

This is what is realistic given your time and the climate (it gets pretty hot in Andalusia so I hope you are going closer to October).
Fly into Seville fly back from either Granada or Malaga (this is the international airport in Andalusia).
4 days in Seville include a day trip to Cordoba and or Cadiz if you want a beach.
Take the bus or train to Granada
3 days Granada include a day trip to Malaga if you want a beach.

Rick Steves did a couple videos on Andalusia if you want to get a general idea of what you might want to see:
https://www.ricksteves.com/watch-read-listen/video/tv-show

With only seven days, assuming those are exclusive of travel days, realistically there’s only enough time to visit a couple cities, e.g., Sevilla and Córdoba or Sevilla and Granada. Depending on what you want to see you could squeeze in a day trip.

Rental cars come in handy when visiting locations not well served by public transportation. With your limited time I doubt you’ll have time to visit any small, out of the way, locations.

As an FYI, it can still be very warm throughout September.

With only one week, I would choose Sevilla and Cordoba; easy to get from one to the other by train.

This is what I would do:

Fly into Madrid, take taxi to Atocha, and take train to Cordoba; spend three nights there, or two nights if you are able to get up and running on the day of arrival.

Take train from Cordoba to Sevilla; spend remaining time in Sevilla.

Fly home from Sevilla with connection in Madrid.

No need for car.

Keep the heat in mind.

If at all possible, take that trip in cooler months and visit northern region(s) in late September: With only a week, consider:

Basque region
Asturias
Galicia

Each one of these regions deserves a bare minimum of one week. Weather should be much more pleasant than in the south.

I get wanting human over AI but consulting a guide book will really help you get familiar before you delve in to specifics. There is usually a section in a guide book that details itinerary options whether you have a few days or a few weeks. I'd flip through one first to see what stands out to you, then post that here for feedback. When you leave it fully open, you get what others would do/did do. You only have a week, so to me that is two stops, three max if logistics require it. Train is excellent for cities and car helps a rural trip. A week in Seville would not be out of the question--fly there if possible if you intend to skip Madrid, but if it is the best option, the train is quick.
First, please get this aspect out of the way: Is the heat going to be an issue for you? It is not for me, but I still would visit a different area in September (unless you mean the very end of the month).

RE vegetarians. How strict are they? I am a pescetarian and I always find it helpful to peruse regional cookbooks. The best dish for me in Andalucia was spinach and garbanzos, and I never felt the slightest bit of missing out with tapas. For big meals, checking menus should suffice. If you all are big breakfast people, I recommend choosing hotel carefully or renting an apartment.

Thanks for all your replies. Sounds Like I need to do more research, but delaying to October sounds like a smart idea. In addition, we were hoping for some coastal time and restricting to Seville and Cordoba will not accomplish that. We could stretch to 8 days, but any advice on getting a couple beach days in? Thanks.

It depends on pinpointing exactly what you want--there is a lot of "city beach" in this area. The sea is not really the draw, so I would not feel bad at all about excluding it when you have the gorgeous towns of the interior. That said, my favorite part is south of Cadiz, where it's a seafood lover's paradise and lowkey. Vejer de la Frontera is not right on the coast but very close and a nice place to stay.
Malaga is a fun city too, perhaps look at flights there?
But priorities and flights will dictate what you have a time for.

I agree with sticking to Sevilla, Granada and Malaga (maybe some beach time). I’m sure there are flights from Malaga to NYC. We did train from S to G and bus from G to M.

For your vegetarian friends: be aware that vegetarian dishes could include fish (at least tuna). So always ask.

There may be direct flights during summer from EWR to Malaga. United.

Just got back and it was 80 degrees in Nov in Seville this past weekend. Does your eight days include travel? Also I would stay in hotels vs airbnbs. The anti tourism in other parts of Spain is about locals not being able to get apartments
Being respectful of that we stay at hotels. Plus they are a great help & can hold your bags on check out day.
Enjoy

Exactly how many nights do you have on the ground? I would prioritize the jewels of Andalucia: Seville (Alcazar), Granada (Alhambra), and Cordoba (Mezquita).

Possible itineraries:
Seville - 5 nights to include a daytrip to Cordoba
Granada - 2 nights

OR
Seville - 4 nights
Cordoba - 1 night
Granada - 2 nights

This assumes you will have 7 nights on the ground. Use trains or buses to travel between each city. Public transportation is wonderful. Driving a car and trying to park in these cities will be very stressful.

This might be useful -
13 Best Restaurants in Seville, From High-Level Gastronomy Spots to Romantic Holes-in-the-Wall

https://www.cntraveler.com/story/best-restaurants-in-seville-from-high-level-gastronomy-spots-to-romantic-holes-in-the-wall