I like that idea better than the Aquarium because driving/parking together is going to be a problem in the city and it will definitely be more expensive.
Gambrill State Park in Frederick has several overlook sites, plenty of room to park, there are several large pavillions in case it rains, dozens of picnic tables and outdoor grills, bathrooms, and a small natural/outdoor playground for the kids. We could also arrange a scenic cruise to Antietam to check out the battlefield if anybody is into civil war history and there's also a pretty cool watch tower we can climb.
07 WRX (Albins 5MT + Blouch 20G)
Jorge Carrillo Tuned (365 whp/340 wtq)