Advice on Spain Itinerary?

Are you flying out of BCN, and are flights already booked?
You can easily buy yourself some time by taking the train to Sevilla on arrival (no need to split the stay in Madrid). It is not a terribly long train trip. See Renfe website for schedule.
I would not choose these four cities in this amount of time, but you have to consider your own personalities--are you go-go-go types? Look at all of the transit time and see how you feel about the days.

yes, flying into Madrid and out BCN. In December we did plane and same day train; it was a long day even with a direct flight landing 8am. This trip already is longer with a layover and I'm not sure we'll have the stamina to add another 3 hours travel time on little to no sleep. And all the trains from Seville and Granada go through Madrid. Flights (from Granada/ seville) were pretty much same time/ more money, if they existed at all.

Gotcha. Been there.
I am the type of traveler that will skip something entirely rather than plan what I consider too much, so I can only offer the activity I do myself--write it out day by day, including all travel time. One full day for Sevilla is very tight, and if you made it four you could easily fill that time. OTOH, two nights is pretty much the minimum for Granada. So, it really comes down to how badly you wish to see the Alhambra.

I actually came up with the itinerary based on the Rick Steve book ;) And I had a friend mirror the city recommendations. I'm likely pulling a day from madrid or BCN to add to the south but not sure which one to shorten. We're from Ohio so definitely keeping the Toledo day trip :)

RE The RS books--if it is based on the tour then it is purposely much more fast paced than independent travel. Make your own list of things to see and do and then see if it all fits. Without knowing what you want to see in each place, it is hard to advise. Have you all traveled together before, and how did it go? (Are you dragging them out of bed or are you all on the same wavelength--sharing these types of tidbits about yourself can help when it comes to advising on pace of travel). Good luck!

I’d add that day to Granada. If you’re all also thinking about Madrid art museums, you’ll want to keep all your Madrid days, to allow for that Toledo day trip as well as the Prado, Reina Sofia, and Thyssen-Bornemisza museums.

Inspired by seeing the bath complex at the Alhambra, really enjoyed getting a soak and massage in Granada at the Hammam Al Ándalus - really recommend you consider going there, too.

I've landed in Madrid ~9am and flown to Sevilla around 11am, and that worked out pretty well. Passport control is pretty quick so it's not very challenging. Obviously, it makes that travel day longer, but it's a time saver.

My general advice is to connect to Sevilla from Barajas on day 1, cut out Granada, and just do Sevilla, Madrid, Barcelona. If you minimize time spent on intercity trains, checking into hotels, and checking out of hotels, you have more time for the actual fun stuff. I would rather split that 3 ways rather than 4 days, and just assume you'll be back to Spain in the future to see Granada.

Passport control is pretty quick so it's not very challenging.

A slight clarification is that passport control is normally pretty quick, but in 2023, flying into terminal 1, it took 1.5 hours to get through immigration. In 2024, terminal 4, it only took 20 minutes. Plan accordingly.

Everyone is different and has different interests. I would not recommend omitting Granada from your itinerary. The Alhambra is magnificent and is one of the most impressive and most beautiful places I have seen. I don't mean to sound morbid, but one can never really plan on returning some place to see a missed site. You just never know what life will bring your way and prevent you from doing so. 2 nights are fine for Granada.

I would also add two more nights to Seville to make it 4 nights. There are so many important historical and cultural sites to see in Seville, and it's a gorgeous city for wandering and exploring.

Have you made your airline reservations yet? Logistically, Barcelona is an outlier. I would concentrate on Madrid, Toledo, and Andalucia, and include Cordoba, another wonderful city that boasts the amazing Mezquita.

Your proposed time in each location is too short, also, you didn't include Segovia, a great day trip from Madrid. It has an intact 1800 year old Roman aqueduct that was in use into the 20th Century.

If you plan to ever come back to Spain, consider skipping Barcelona this time and add more time to Madrid and Seville.

Be sure to do Toledo, it is my favorite.

Rick Steves recommended itinerary and pacing is efficient, commonsense and practical for most travelers. Experienced travelers who've made many trips to Europe and are older generally recommend slower pacing than Rick and their advice fits well for those travelers who like themselves are into savoring the experience rather than trying to get the greatest hits.

When we took our college age kids to Europe, they thought Rick's pace was actually too slow. As I age, I find I too often like the slower pace. All of this is to say I would recommend as a default to take Rick's advice and then tailor or tweak it to match your style and interests.

Happy travels.