If your family doesn't like the idea of a treated lumber wall, perhaps a stone one would be more attractive. You don't say if you will be doing the work yourself or if it will be done by a professional. I would advise the latter if money is not a problem. There are lots of different materials that can be used according to your taste. These include dry walls, mortared walls, brick, and interlocking concrete among others. Go to the library where you will find several good books, such as Garden Walls, Fences and hedges by Kathy Sheldon (2002) with illustrations and instructions. This will not only give you ideas, but perhaps settle any family discussions!