How unique will our baby be? :)?

congrats, i wish your little family the best. as the marjority of his heritage (5/8) is vietnamese its most likely thats the race he will most resemble. as for accent, where do you live? he will have the accent of the community in which he lives.. when learning to speak he may have a bit of a mix of Aus/USA accents but as soon as he starts preschool and school, and starts interacting with other people and children in the wider community he will quickly take on that culture and way of speaking.