Bird flu hasn't been a problem so far in the United States so there really isn't anything that you need to do. It hasn't been a problem with pet birds either. The human cases were in people who had a lot of contact with infected chickens and other domestic poultry, and those birds might have caught it from infected wild ducks. If the virus ever does make it to the US, your birds won't be at risk for catching it if you keep them away from places where infected wild birds may have been. There's probably more of a risk that the humans will pick up the virus somewhere outdoors and bring it home!
Here's a good article about it:
http://www.webmd.com/cold-and-flu/what- ... t-bird-fluThere are half a dozen countries where bird flu has been a problem, and unfortunately Vietnam is one of them. I don't know whether your family ever goes there for a visit, but if they do then that's the place where they have to be careful.. Your pet budgies aren't any risk at all as a source of bird flu, but the chickens and ducks in certain countries could be a problem.