How terrible for Charlie and your whole family
I'm so sorry!
I agree with taking the dog's owners to court for the vet bills, and for money to purchase another baby (when you're ready). It won't bring Charlie back, but it COULD make those people think twice about letting their dog run around off-leash ever again. A stupid little citation won't do that, they'll just pay the small fine, but if they have to come up with a substantial amount of money, court ordered, maybe it will open their eyes.
Again, I'm so sorry for your loss, and for the obviously traumatic way that it happened. My first Yorkie, Starr (RIP) was attacked in the same manner, though she survived her injuries (she passed from something else later on), so I totally know how terrifying that had to be for all of you. Sending you warm hugs! RIP Charile