Threat displays by elephants include: turning towards you, spreading ears, standing tall, head-nodding, head-jerking, head-shaking and head-tossing, forward trunk-swish, demonstration and real charges.
To better explain the afore-mentioned:
Head-jerking is a single, abrupt upward movement, followed by a slower return.
Head-tossing is a pronounced version of the jerk, the head is lowered and then lifted sharply so that the tusks describe and arc.
In head-shaking, the head is first twisted to one side, then quickly rotated from side to side, causing the ears to slap against the face with the sound of a snapping towel.
The forward trunk-swish, typically accompanied by trumpeting or and air blast, is a threat usually addressed to a smaller antagonist. The trunk is rolled up and then abruptly unfurled ans swished toward the antagonist. Using the same gesture, elephants sometimes pick up or rip up and throw bushes, grass or other objects towards the antagonist.
Standing tall is a dominant display, resembling the alert posture, but the head is raised higher and the elephant peers over it's tusks, ears cocked and trunk hanging at an acute angle.
Spreading of ears and holding them tensely forward or flapping them is a clear indication of defensive behaviour.
I have also heard and read somewhere, that when an elephant means business, it nearly always comes immediately and without warning, except for a momentary rocking motion of its body, sometimes even without a sound. The tail stiffens, the tusks are held high and the trunk is drawn in against the chest. The ears are usually, but not always, spread to their full extend giving the head a most awesome frontage.
Elephants can also be timid to a point of absurdity. A large bird landing nearby, the presence of a squirrel or a mongoose blocking the path is often enough to alarm them, and sometimes the whole herd will bustle away from a purely imaginary danger. (So I think the toy mouses attached to the car will do the trick
But, you are on vacation, do not worry about what may and what may not happen with the ellies. Just be careful and give them and yourself some personal space and enjoy the ride!