Itinerary for 11 nights - Madrid, Granada, Seville

In Madrid, you may not want to see the two museums in one day. The Prado is quite overwhelming (and crowded), and merits a several hour visit. You will probably be done for the day with museums at that point, especially as you will be there with kids, and will enjoy the walk in Retiro Park. The Plaza Mayor and the Puerto del Sol are very touristy and not really places to linger, in my opinion, so maybe you could get the other museum in that day.

You will probably want to book the Alcazar in Sevilla in advance. Especially if you want to see the Royal Apartments, which you book for separately. When we were there, it was sold out, and people were milling around very disappointed they couldn't get tickets.

Your itinerary looks very reasonable to me. I do agree though that 2 museums in one day is too much especially with little ones.
Nowadays, with the increase in tourism, I think that one should prepay for tickets for any sites that one can. For one thing, sometimes it's cheaper to buy the tickets online. For another thing, the lines for the box office to buy tickets in person can be long and the wait can last an hour or more. Also, there are some tourist sites ( such as Edinburgh Castle) where you can only purchase the tickets online.

Don’t go to the free visiting hours at either museum. It’s not worth it. The Prado especially gets very crowded, I would really prioritize going there exactly when it opens, on a lower traffic day if possible.

Book Alcazar tickets for sure.

I would think about your Madrid schedule again once you have lodging booked. Are you doing Airbnb or an apartment rental? You might figure out a more efficient way to split it up once you know what part of town you’re in for the evening.

No idea about the economics for traveling as a big group.

I have food and wine recs for Madrid and Sevilla if you would like.

I have no experience traveling with children, but that's a large group you have. I would wonder about availability of the necessary car seats and being able to fit them--and your luggage--into a vehicle that can be driven by someone with a standard driver's license (though I don't know Spain's regulations on that score).

Driving into the center of Cordoba in a large vehicle could be quite the experience. I once saw an SUV trying to traverse one of the narrow streets in the historic center. The side-view mirrors were folded in, the wheels were rubbing against the curb on both sides, and the car appeared not to be moving. I was walking in the other direction, and I had to reverse course and walk around the block, because the narrow sidewalk wasn't safe for a pedestrian.

I think you'll be a lot happier taking the train. I agree that you can't count on finding lockers free at the Cordoba bus station (very near the train station) by the time you arrive from Granada, but there are multiple options for luggage storage in Cordoba. Some of the storage places require online booking in advance, but that way you know you have a spot. Three companies that connect travelers and local storage options in multiple cities are Radical Storage, Stasher and NannyBag. There may be others.

Rail fares from Granada to Cordoba to Seville and from Madrid to Segovia are variable. You'll save money by buying tickets well in advance, but pay attention to the cancellation/change policies. The earlier you buy, the more important it would be to pay a bit more for Elige tickets that can be altered.

Spain is a country where express trains sometimes fill up. If you're traveling during a holiday period in Spain (Easter? some local holiday?), the risks are probably higher. I've observed "Full" indicators on lots of trains on the Barcelona-Madrid-Cordoba-Seville route and the Madrid-Toledo route. I don't know about the Cordoba-Granada leg, but there aren't all that many departures, so I wouldn't leave that purchase until too late even if I were not trying to save money.

Although I haven't had trouble paying for train tickets on the Renfe website, others have reported issues in the past. If you run into that roadblock after trying all your available credit cards, you can get the tickets from TheTrainline.com. There will probably be an additional fee, but it will not be too large, and you'll still come out way ahead because of what you save by buying early--not to mention that you will not risk running into a bunch of sold-out trains. TheTrainline sells tickets on Iryo trains as well as Renfe trains.

In addition to the spots already mentioned, you should prebook entry to the Seville Cathedral. As with the Alcazar (and that includes regular tickets, not just entry to the royal apartments), the ticket line is usually extremely long, and it is outdoors. Aside from the royal apartments, I don't think those Seville sights sell out really early; you just need to avoid the very time-consuming ticket lines. There will be a line minder at each place, so you can just show up with your tickets in hand (or on your phone, I assume) and get directed to the short line for people already holding tickets.

The Prado and (if you're interested) the Royal Palace in Madrid are two places where some folks suggest buying tickets in advance. Neither was a problem for me back in 2016, but more people are traveling now. The Royal Palace seems very popular with Spaniards, so if you are traveling around Easter or another holiday period, you could run into quite a ticket line there, I would think.

We are not serious art people, so we were thinking just spend 1-2 hours each at the Prado and Reina Sofia. Not sure if that's possible if just to see the highlights. But it may make sense to just go during non-free hours so we can quickly go through the museum anyway.

We are staying in a 3 bedroom apartment rental near Plaza Mayor the first 5 nights in Madrid, and we're staying in Plaza de Santa Ana that last night before we fly out. Food and wine recs would be great.

For Seville, we are not there during Holy Week, but we will pre-book tickets to the Alcazar, Royal Apartments, and Cathedral as you suggest.

If we stop at Cordoba via train, I assume we buy 2 separate one way tickets - Granada to Cordoba, and Cordoba to Seville. There is no cheaper extended stopover ticket from Granada to Seville? I will look into those luggage storage companies. It does seem easier even if we have to lug our luggage 10 minutes down the road. The other option was to go to Cordoba from Seville as a day trip but it doesn't seem efficient to back track? By the way, how long do we realistically need in Cordoba for Mezquita, lunch, and Jewish quarter?

Do train tickets just keep going up in price as the dates get closer? We're going in March. Or is it good to wait for a sale?

Train tickets go up in price as time goes by, not down.

The last time I went to the Prado in 2022 we went during the free hours. We got in line about 40 minutes before it opened. We were given a ticket with an entrance time, but the people at the door didn’t strictly adhere to the time. Once the doors opened, we just went in with the crowd. Not being museum people, two hours was sufficient. I will add that we had been to the museum two previous times. The museum was crowded, but not more than it would be during the regular admission hours.

For the Reina Sofía we got in line about 30 minutes before it opened. Once the doors opened the line moved very quickly. I feel two hours is sufficient to see that museum. That was in 2011 and the museum might be more popular now.

Going during the free hours definitely can save you money. Since the free hours start about the same time, you’d need to choose which one to visit. I can’t imagine paying to visit the museums just to rush through them to check the I was there box.

If you’re not art people maybe just skip them. Only go to places you have a desire to visit, not because someone says you should.