Plenty to do on a Sunday night in Baltimore -- lots of dinner options and activities around the Inner Harbor and immediate surrounding areas.

In terms of Monday morning (Labor day), not sure what will be open. The main tourist attractions at the Inner Harbor are the National Acquarium, Maritime Musuem/USS Constellation, or a boat ride out to Ft. McHenry. But there are also a lot of other cool places within walking distance like the Babe Ruth Musuem (if you are a baseball fan). Other cool places are the Edgar Allan Poe House or B&O Railroad musuem, but those will require a cab ride and not sure you would have time.

Here is a list of major attractions -- http://www.ci.baltimore.md.us/visitor/