Keeping in mind that there aren't really "resort" hotels/motels on Harbor, some are nicer than others. The Fairfield gets good reviews, and so does Marriott Courtyard (can't remember the full, correct name)... However, if they plan on spending most of their time in the parks with your family, and just need the room for sleeping and showering, we've stayed at Park Vue Inn (PVI), and Tropicana, and really liked each of them. Admittedly, we tend to stay at Trop more, because they are about $50-80 less a night, and love their new decor.
PVI was renovated back in 2013 or so. Their paint scheme in their rooms is what I would call a "southwest" palette. Beds are comfy, rooms are average sized, and they have a great breakfast spread (which varies day-to-day). I have no idea if/where they have an elevator, if stairs may be a problem. Their hot tub is nice; its in the middle of the parking lot, but has a brick and ivy fence, so it feels a little more secluded in the evenings/night.
Tropicana finished their remodel at the end of 2017. Their rooms now have kind of a Cali-surfer vibe going. Blues, dark brown furniture, some orange accents. Beds are comfy, bed linens are comfy, towels are sufficient. We've fallen in love with their King bed rooms up front, near the elevators. Our last room there only had a shower in the bathroom, but, for adults, this is pretty reasonable. No free breakfast here. Pool and hot tub are in the parking lot. I've never used them at Trop, but not for any reason; just haven't made a point of it.
Best Western Park Place is right between PVI and Trop, and people seem to like it as well.
