This pizza place is right around the corner. I haven't been there, but I have friends who live in the building and they say it's good. I think it would definitely work for a quick dinner with kids
http://baltimore.twoboots.com/

I've had some good soup at Soup's on (although they undersalt everything)
http://www.soupsonbalto.com/

There's a Chipoltle on Charles Street, and basically if you walk a few blocks south on Charles from the Lyric, there are a lot of places to eat (and of course there are nicer places with more interesting food-like Helmand, but I'm assuming OP wants something quick and kid friendly).

We are going to the 5:30 show tonight at the Lyric in Baltimore. We are looking for an easy place to eat fairly quickly before the show, preferably close by. Any suggestions?