How to best beat an opponent in the minecraft LOTR mod?

My nine year old son is obsessed with fighting me in a flat world server, equipped with the LOTR mod. He wins every time. It's like he s invincible. How can I get an advantage over him? Since the world is flat, its hard to hide. Also, we play in creative until we re ready to battle - we set up bases before we turn to survival. What are some good weapons/strategies for such a game? Yes, I'm a mom of 35 wanting to kick *** and I d love some help!