Having played a bit with the resort, one of the things I found helped out was having 3 buffet tables. One I rotated through the day of breakfast, lunch, and dinner, one I rotated vegetarian, sushi, dimsum and the last I rotate between kids (daytime) and dessert (evening). a bit of micromanaging through the day, but the food reviews have gone way up.
And I found that the stained old tub at the free starter resort Hobart's Hideaway sells for 1000 simoleans, a nice infusion of cash to get those buffets rolling!