Galvanized Pipe - Bathroom Remodel

Hello Everyone,
Sure hope you can help me out here. I'm helping out my brother-in-law remodel his first floor bathroom and I would like your input on what we should do with the old galvanized water pipes. Let me try to describe the scene as best as possible. The home is a two story house with a crawl space. The first floor and second floor bathrooms are right above each other. The water supply lines for both bathrooms are running between the first floor ceiling joists and branch off with tees. Leading from the ceiling down (vertical run) to the first floor bathroom are 1/2" hot and cold galvanized supplies, which are currently capped.

We are looking to rough-in supplies for the lav, toilet, and shower. Normally not that big of a deal, though when you throw in a wash machine in the mix which is located on the opposite wall, how should I attempt to rough-in the supplies? Here are the only two options I can come up with...

Option #1: I really would like to join a copper/brass dielectric coupling to the existing galvanized tee, and the run new copper supplies within the ceiling joists to the new wash machine outlets. The problem is that I cannot use wrench to tie in a coupling for the galvanize pipe, let along sweat the dielectric union fitting to copper. Totally inaccessible.

Option #2: Tie into the galvanized supplies with dielectric couplings that are about 4' from the floor and run copper through notched out studs to supply the new washer.

I've always understood that in order to tie gal to copper, you need to use a dielectric coupling. Also, I am concerned that if I choose option two, and given the fact that the supplies are currently 1/2" that water pressure may not be the greatest for the eventual new lav, toilet, shower, and wash machine.

I apologize in advance if my terminology isn't up to par, though whatever insight and options you might be able to provide, I'd greatly appreciate it...

Thank You!

First, don't confuse volume and pressure...you'll get the same pressure out of a soda straw, but the volume would be much less than a fire hose being fed from the exact same supply. Were it my house, and I was remodeling, I'd tear out all of the galvanized and replumb it. Galvanized is no longer used for plumbing water supplies for good reason - it has a limited lifetime, and in the process of failing, it slowly decreases the available flow (volume) as it rusts from the inside out. Along the way, it will start to get some pinhole leaks before it literally decomposes into a heap of rust. The hot water usually goes before the cold. Now, what type of pipe to replace it all with is up to you...some prefer copper, and it is a good choice. Pex may be easier to thread through the walls since it bends. 1/2" supply for a full bathroom group (well, sounds like two of them) plus a washing machine is just too small for good performance - it would be very easy to exceed the flow capacity, and then you'd notice slow filling of the tub, and marginal operation of the shower, if more than one fixture was running at the same time.

This is a pretty big first time project for a beginner. You'd be wise to hire a plumber (NOT a handyman that says he does plumbing)

Code likes the dilectric unions, however they close up rather quickly. I would never hide one in a wall. I prefer to transition with 6" brass nipples. It slows the corrosion. Best, is to pull out as much galvanized as you can now. Sooner or later it will need to come out.
You can really only run two fixtures on 1/2" pipe. Certainly not a bathroom and a washer. A washer is not friendly to the other uses. It's kind of a water hog when it comes on. If it cycles on when someone is in the shower, the shower will lose that battle.