Actually last night we did exactly that, we decided to "divide and conquer", so we took them on separate training walks. We realize we will need to do some training work. Going for walks when we only had one dog was fun for us, but we realize now that we are going to have to do some work with the dogs separately.
This is exactly what you need to do!
Here are some good videos about building focus around distractions and leash reactivity.
You've gotten some excellent advice so far.
I would add my vote to the 'long line instead of muzzle' camp (although I think a bit more attention work and good greeting behavior should happen first). Muzzles are a good tool when they are necessary, but I always think of them as an absolute last resort (and the dog must always be conditioned to them first) because they have a tendency to make reactive dogs more reactive because they feel vulnerable.