Hi S.....
I tend to agree with the last response. If you have family that is close, see if they would be able to watch baby forthe day/evening. If not, then someone close like a good friend that you trust. It was really hard for me when my oldest was 7 months. I didn't have that connection with anyone yet.
Are you on the Eastside - Bellevue/Redmond/Kirkland area? At 7 months old the Pacific Science Museum is a bit old, except maybe the butterfly exhibit. Any of the Children's museums with water tables, sand rooms, textures and sound exposure would be good. The one at Factoria Mall is really neat! We live on the north end so we go to Imagine Children's Museum in Everett.
And of course the zoo and the aqaurium would be great. The aquarium completed that big addition/remodel and it is really amazing. If anything you could go downtown for the day. Lunch, aquarium, shopping, etc. Could be a lot of fun. Your son will get to smell the salty air, and see/hear the seagulls and see LOTS of people. I remember taking my daughters on a ferry boat ride. They LOVED it, even at 6 months old.
I wish you lots of luck! What's important is that you will be spending quality time together as a family. That's what will make the biggest difference to your son and also to you and your husband.
Take care
A.