If you want to use them, then use them. I've heard so many bad things about RealGap, but I think it depends on the place. But Vietnam is lovely and cheap. There's not that much planning involved really. Just start at one end, and get a bus/train/plane to the other. Vietnam is very easy to get around especially when it's not the rainy season, when some areas are hard to get to. You'll learn a lot more from doing it yourself rather than going by a company. But if your dad wants you to go realgap, you don't really have much choice. It isn't unsafe though.