How can I word a sign?

We have a mobile food truck that is made from a converted fire truck. Kids love to climb on it and pull and push the nonworking buttons and knobs. I don't want our company to be held liable for any injury that could happen from on or around the truck. How can I word a small sign to cover all liability. What are the exact words to write that would stand strong against any accusation of liability. The sign I am thinking is "(business name) is not held liable for any injury from climbing on the Firetruck. Climb at your own risk". Is this sufficient to cover and protect us from all possible liability issues?