Probaly he will not be afraid, just tell him it's like flying.
Anyway, you can take the shuttle bus from one entrance to another (ask the staff), most of the time you have to pay ~$3.5 per person, unless at the time Ocean Park think the cable car queue is really too long, then the bus will become free.
手背蓋個章 is for you to leave Ocean Park, say to Aberdeen for lunch, and want to return later. If you just want to take the shuttle bus to 大樹灣 entrance, there's no need to exit the gate.