What I thought when DH said he wanted to take a three-year-old to a real, grown-up concert:
It went okay, though. We picked our seats carefully (in a box, near an exit), and watched this video to prepare (a little dated, but the footage of manufacturing the various instruments was of great interest). The Bean made it all the way through to the intermission no problem, and probably would have made it through the whole thing, had he not gotten his head momentarily stuck between the back and seat of one of the chairs just before the beginning of the second half. It was just for a second before I extracted him, but enough that he was too upset to come back in until the Hallelujah Chorus.
He's pretty enthusiastic about pointing out the instruments in the orchestra now, though, so we'll call it mission accomplished. Even though I'm pretty sure that he thinks the opening recitative is "Come For Tea."