If you go to Chaps Pit Beef, definitely get the Tiger sauce on your beef (its horsey mayo). They've also got a sandwich that is half pit beef, half sausage that I think is even better than just the beef.
If you are a craft beer lover, there is a good craft beer bar a short walk from the stadium called Alewife that usually has a pretty good tap list. A short drive north, further away from Camden Yards and your hotel, is Brewer's Art, an upscale brewpub which wins national awards for making great beer. They make great beer. Others mentioned Fells Point and there is a great craft beer bar that is listed in the top 100 in the world for craft beer yearly called Max's on the Corner. Tons of taps, maybe 60 or more by my memory, tons more bottles of special stuff.
Maryland Blue Crabs are in season. I think the best crabhouse in Baltimore is Bo Brooks, which is down on the way to Fells Point from Inner Harbor. You can get a dozen steamed Maryland blue crabs and that will feed a few people. Others swear by Obryzki's, which is a more upscale crabhouse in downtown.
If you take the family to the aquarium, I recommend just signing up for an annual family membership, which is maybe a couple bucks more than just getting single visit tickets but allows you to go right in and not wait for a specific time to get in. If you get single visit tickets you typically have to buy them for entry at a specific time a couple of hours later due to lines. If you get an annual membership, you walk right in with no wait. It really isn't much more at all. As you can tell, I'm an annual member and have only visited once.
Near the aquarium, there is a boat or submarine you can enter and tour. It is one of 5 maritime vessels in the area you can enter and tour as part of a package. My kids of 7 and 9 were interested and not bored by it.
Fells Point is the center of nightlife in Baltimore -- not kid friendly -- all adults, good bars and restaurants. Downtown Baltimore is not a good place to be after dark and don't walk from place to place downtown after dark once you get out of the immediate area of the stadium or Inner Harbor. I'm not kidding. I stayed twice last year at the best hotel downtown called Hotel Monaco. Nice hotel. At the end of the block after dark there was a group of female prostitutes and a block further north was a group of male prostitutes. A block north of that there were drug deals being done openly from cars doubleparked in the two lane road so that if you went up that street, you had to stop and wait for the car ahead of you to finish what they were doing and drive on. Big drug problem downtown and with that there is crime -- theft, muggings. I happened to be there on Easter and had to drive through that area to get to a Rite Aid to buy baskets and candy for the kids late on the Saturday night before.