2 Week Spain Itinerary with three 18-20 year old young men

I opt for tiny single rooms that wouldn't be suitable at all for groups of two or more. I'd suggest looking at what's available on booking.com to supplement suggestions you receive here. I like the booking reviews because only folks who've stayed at a property can review it.

Your trip has a southern tilt. It's likely to be extremely hot, though you may get lucky in Barcelona. Pay particular attention to what reviews say about the quality of a hotel's air conditioning.

Madrid weather -- June 2023

Seville weather -- June 2023

Use the pull-down box at the right, just above the graph, to change the month and year displayed. I normally look at the most recent five years, because weather can vary a lot from year to year. Use the Search box at the upper right to change the location.

Miserable though the weather is likely to be in Seville, I think you're shorting that city on time. I'd rather have 3 days in Seville than 2 days there and 1 day in Ronda. It's not that I dislike Ronda; I've been there three times. It just doesn't hold a candle to Seville. Or to Cordoba, which you are skipping.

Active young adults on a trip to southern Spain would probably be interested in walking the Caminito del Rey, but I don't know how practical it is to get there without a rental car.

Caminito del Rey

How handy to have young backs to help tote the luggage. And also young appetites; they should know that dinner is served very late in Spain. It comes with the fine Spanish wine which they are allowed to drink.
In advance, they could take on the computer task of investigating Granada. The sacred buildings there are more interesting if the religious requirements of the Muslim faith are taken into account. And also the engineering skills to build a temple around water in a dry area. With a wider horizon, they might be surprised at how many different areas they will see; Spain's history is the story of division as well as nationalism.
PS: There's a series of amusement parks named Ferrari? I was thinking expensive race cars. But no, that's Italy. Spain's
car brand is Seat, now a part of the Volkswagen stable. Zippy, though, and pronounced with two syllables.
Have fun.

Based on our trip last September (though we are on the opposite end of the age spectrum from your young men!!), I highly recommend walking the El Caminito del Rey and the rooftop tour of Seville Cathedral. We had a car but there are day tours from Malaga to El Caminito del Rey. We found Ronda to be overwhelmingly crowded and uninteresting. Maybe take that day, add it to Seville and take a day trip to Cordoba to see the incredible Mezquita. And, while in Seville, try to go to Bar El Comercio for churros!

You've got enough time in Málaga to permit you all (or preferably maybe just the boys) to take the metro out to the cheesy beaches in Torremolinos and Benalmadena. They're really not to be missed for teenage boys visiting the Costa del Sol.

Hi, no idea how they celebrate San Juan in Granada - but I'm absolutely certain it doesn't involve any beach activities.
I would venture that the youngsters in your party would very much more appreciate and enjoy spending Sant Joan in Barcelona. Wild. Much more wild. Guarantee it. Based on your current schedule you'll arrive in Barcelona two days after the big summer party is finished, ah well. Enjoy a dismal Sant Joan in the south.

take the metro out to the cheesy beaches in Torremolinos and Benalmadena

That is not correct. You use the RENFE Cercanias Line C1. The Malaga metro is a tram network within the city of Malaga. It is totally different to the Cercanias suburban railway lines.