I moved here from Florida several years ago. My wife and I have a kid now (didn't at the time of move) and we have lived in city and outside of city. I've been all over the country and for me the Pacific Northwest far exceeds any other place for livability. It is stunningly gorgeous. I can actually go outside in the summer and do things without desperately wanting to get back indoors and cranking up the AC. The city of Seattle is great - I feel safe walking around there (despite what others may think, relative to the downtown I am from, Seattle is safe). I love that I can get up in the morning climb a mountain up and down and within an hour I can be back in the city watching a movie or doing whatever. The proximity of outdoor/nature stuff to city stuff is great. The public transportation here rules compared to Florida. As for the "SAD" thing, my wife and I personally have not experienced this, but I think we embraced everything about the PNW including the weather. You start to realize many benefits of the rainy winter season, like hiking offers much more solitude in the winter, you can go snowshoeing, you can ski/snowboard, etc. The other thing here is, rain here isn't like Florida downpours (usually anyway), its totally tolerable, just get a jacket and don't let it stop you from being outside. Someone in a past thread said "The rain sort of just exists around you," I think that is a good way of describing it.

Also, I agree with others who say you can raise a kid in or out of the city. I live in North Bend now, and I love it because I have over an acre, privacy, access to outdoorsy stuff, etc., but Seattle has lots of great neighborhoods as well. You just have to visit and look at all the different options and find the place that feels right.
Good luck.

I agree with comments that you can raise a kid