|Dwarf Mondo Grass Lawn|
Lawn grass is popular because it tolerates a high degree of foot traffic and can be mowed to a low height for outdoor activities. Furthermore, it covers quickly and relatively inexpensively. But it does require frequent maintenance.
Dwarf mondo grass - Ophiopogon japonicus 'Nana' - is a fine lawn substitute. It tolerates foot traffic, providing you don't regularly play team sports on it. Walking about is okay. It has a naturally low profile, so doesn't need mowing. It covers densely. It is cold hardy in your area. It is drought tolerant. Color is deep green. It thrives in partial shade to full shade, so that might be a disadvantage to you. Other disadvantages include expense of establishment - i.e. plant cost -, and it is slower to spread than lawn grasses. The plant cost would probably be offset by low maintenance cost over time.