I mentioned the Menger Hotel, but another famous one in San Antonio is the Gunter Hotel. It's where Robert Johnson had his famous recording session. If your son has an interest in music, it would be an interesting side trip. On Houston Street, downtown. Within walking distance of the Alamo. Been a while, but I think it's 4-5 blocks from the Alamo:

"...Speir, who helped the careers of many blues players, put Johnson in touch with Ernie Oertle, who offered to record the young musician in San Antonio, Texas. At the recording session, held on November 23, 1936 in rooms at the landmark Gunter Hotel which Brunswick Records had set up as a temporary studio, Johnson reportedly performed facing the wall. This has been cited as evidence he was a shy man and reserved performer...

Among the songs Johnson recorded in San Antonio were "Come On In My Kitchen," "Kind Hearted Woman," "I Believe I'll Dust My Broom" and "Cross Roads Blues."

http://en.wikipedia.org/wiki/Robert_Johnson_(musician)

Going through family photos I found the one at the link below. An uncle on my mother's side, about 1941, 5 years or so after Johnson's recording session. The Gunter in the background:

http://mail.moment.net/~michael/Gunter.JPG