You'll have plenty of good food options available in Edmonds after visiting ACO. Ristorante Machiavelli recently opened up after shutting down their Capitol Hill spot, and I really like it (check their hours, though). The waterfront in Edmonds is nice to hang out at, and the downtown area is pretty walk-able. You could also go as a walk-on onto the ferry there and enjoy the Kingston area.
Closer to Seattle is the zoo, Discovery Park, the Arboretum and Japanese Garden, the Museum of Flight, might be able to catch a Mariners game, and this doesn't even touch the Eastside which there is also a lot to do (East of Lake Washington). If you like playing board games you could go to Mox Boarding House (Ballard or Bellevue), you can have a bite and drinks while playing one of their available games. There's the Pacific Science Center, which also has a big IMAX theater. If you support non-commercial radio then KEXP's Gathering Space might be worth a visit. Loretta's Northwesterner has some great tavern-style burgers.
There's really a lot more to suggest, also might depend on your weather-appetite. Bring layered clothing, and a rain jacket (shell type is best that you can stow away easily).