Huertas will be a great neighborhood for a history-minded boy. You are close to many museums and other historical cultural attractions. (Just walking around and admiring the architecture is fascinating!) One other thing in addition to a Real Game that you might consider is taking a stadium tour. It is awesome to go behind the scenes there. The Bull Ring also has a tour, although since it isn't bullfighting season, I don't know if the tours still run.

I've stayed at two different places in Huertas. One is the Hostal Persal. It's a hostal, but feels much more like a nice hotel. The other is the Hostal Jaen which is more like a hostal, including the lower price. There are lots of places in that area to stay. I'd recommend either of my two, although if budget isn't a big concern, probably the Persal over the Jaen.

Trains are a wonderful way to travel in Spain. I've never driven much, so perhaps others will comment. The trains generally take you into the city center or close to it and public transportation is plentiful and economical.

I think your son will love Spain. Keep us posted.