Sunken trampoline in landscaping, surrounded by mulch. Mulch is supposed to be a safer landing surface, since it has more give than grass on dirt in case the kids over-jump. It also blends into the garden area better.
partially sunken trampoline.... I would consider this. this might be good. I don't like the fully sunken ones though because you have to have such a deep hole, and you need vents for the air to escape or else it won't bounce.