I want to personally recommend Musica Antigua de Albuquerque's concerts, especially for anyone studying medieval/Renaissance history.  They are a very talented group of musicians (though I am biased, my husband is in the group), and the concerts truly transport you to a different place and time!  The concerts are open to kids, though it would be best for an older kid (or just a patient kid).  The music is generally quiet, the concerts usually around 2 hours with an intermission.  The programs are really well done, so there's lyrics and other info to read while listening.  I went this weekend- it's their annual Christmas concert- and it was really beautiful.  

Prices:
General $16
Seniors $13
Students $9
Children under 12 $6

Website: http://www.la.unm.edu/~davies/MAA/MAA-home.html

Programs: