no problem for that area. ive done it on a 15m long corridor before. heres wad they shud do. pour susu+adhensive cement 10:3 n make the surface coarse using trowels or just broom. leave it over night. make sure the new floor height isnt too high as the screeding might be a problem if they mix in too much sand (might be too hollow) if its just directly on top of the old tiles, it shudnt be a problem with the right cement mixture used.