Clearly, an open house in bad weather country can get "touchy." Some parts of N. Cal get a lot of rain but all I hear down here is "drought, drought, drought." FINE. That means we got a lot of clear days to rock 'n roll with no worries about rain filling the trenches or ruining the framing. Don't even have to tarp the structure !! WOO HOO!
A simple bump out is manageable as a DIY "IF" you already have some hand's on knowledge and experience. You might want to hire a helper (retired carpenter?) to guide you. Remember, you will need a lot of new tools ... where are they coming from? Precision is important ... can you measure twice and cut once? Can you develop a reasonable project timeline and get materials and help on-site as needed to keep things moving? Nail gun or screws? How high is the typical outlet? What is the proper framing for a wall, door, window and drywall corner?
OH MY ... so much to learn ... hope you have a strong marriage!