Nihonjin1051 is right. If China were to fire the first shot, the best we could do is actually move our navy there and surround the firing ship. If the ship keeps firing, then we can sink it and both Vietnam and China go back to quarelling. If the ship tried to run away, then we could immobilize them, capture the ship sailors and use them as chips to negotiate with China. Either way we should avoid war. Remember Vietnam should never be the one who go around and start war.
No one in East Asia wants war. Objectively and honestly, even in Japan the people are very divided with Abe and even the notion of 'collective self defense'. A lot of Japanese civilians are weary of getting entangled with wars. That is the truth.
The United States does not war either; i currently am in the US and have a lot of American friends as well as talked to many former vets from Iraq and one thing they relay to me in any conversation about battlefield experience is the notion of war weariness. Not to mention the economic toll that a war would have on the United States.
I've been to China many times; most for cultural and touristy stuff (LOL! ), and i've met many Chinese people and get a general feeling that overall Chinese are very warm and receptive. They are too busy trying to improve their way of life, family health etc. Like any other person. War is the last thing they (i assume) they want.
For the Philippines and Vietnam; i am sure that the majority of their civilians feel the same.