I think your basic concept is logical. However, due to travel time from town to town, I don't think 4 or even 5 days is enough to hit all of Seville/Cordoba/Ronda/Granada, given that every time you change hotels you lose at least half a day--and going to and from Granada may take longer than that. Seville and Cordoba are easy. They're right on the AVE line out of Madrid.
By "right away", do you mean you'll take the AVE south on the day you land in Spain from the US? That is a very efficient plan and good use of a period when everyone except your student son is likely to be too jetlagged to do much sightseeing. But figuring out the timing of those train tickets will be tricky. You will probably want to buy them soon to avoid paying the full walk-up rate. (Check Renfe.com to see how fares look as of now for your arrival day.) But the best deals are on non-refundable/non-changeable tickets, so the tickets will be worthless if your inbound flight is seriously delayed and you haven't built in enough lead time to get from the airport to the train station. Atocha Station is a bit confusing; it will help if your son is already an expert at navigating it.
Your son could return to Madrid after 1-1/2 days while the rest of you stay in Seville a bit longer before heading to Granada for two nights. That's the minimum time you'll need if you want to see the Alhambra. (Investigate tickets immediately; they may well be sold out on the official website, requiring special action on your part.) If you don't plan to see the Alhambra, I would skip the rushed visit to Granada on this trip.
Granada to Cordoba isn't too bad a trip; whether you have time for Cordoba depends on how much you want to do in Seville and Granada.
I don't think Ronda is in the cards this time, unless you drop Granada.
Edited to add: I believe Toledo and Segovia are the best side trips from Madrid for your family. If you aren't much into art, you don't necessarily need a lot of time in Madrid. The Palacio Real is a palace rather than a castle; it may or may not appeal. A few of our posters have found time to go to the Naval Museum in Madrid and liked it. That sounds sort of like a "guy" thing to me, so might be good for your family. I remember reading that one needs a passport to get into that museum.
Barcelona is tourist-swamped year round. If your target list for that city includes any of the following sights, you should investigate advance purchase of tickets. Otherwise, you may be spending precious time in long lines and perhaps missing out entirely:
La Sagrada Familia
Parc Guell
Casa Mila (La Pedrera)
Casa Batllo
Picasso Museum (often packed to the gills even after you get inside; consider skipping)
Palau de la Musica Catalana
Seeing a bunch of the most popular sights in Barcelona during a short visit is a real challenge. How much time will each sight take? How long will you be in line--even with a ticket--before you get in? How long will it take you to get to the next sight? It's really like putting together a jigsaw puzzle. Make one of those tough sights your first stop each morning. That will make things a bit easier.
I really liked the Barri Gotic walking tour offered by the tourist office, but I'm not sure what times it is offered. It many have been only at 10 AM when I took it in 2016.