Sometimes I've heard terms last requests, final requests, or final wishes used. These aren't necessarily legally binding, like a will, but they are a way to let wishes be passed along to family members.
Sometimes you'll hear about someone getting their "affairs" in order. In this context, "affairs" would cover a will, along with final wishes, and perhaps even arrangement for a particular a burial plot, an epitaph for a tombstone, indications of whether or not the deceased would prefer to be cremated, etc.
A number of funeral homes use terms like "final requests" or "final wishes" in their websites, as do other funeral planning guides, such as this one.