10. Purchase spare trousers, with an eye toward having a variety of colors in one's wardrobe.
9. Jump into water. My friends know that it is always bad in my games to wind up "in the drink," as we call it, whereas my kids are still learning this the hard way. As of today, they still joyfully leap into turbulent, subterranean rivers.
8. Float downstream in an umbrella. Heck, even purchasing an umbrella is something you don't usually see.
7. Loudly proclaim their royal heritage within earshot of armed thugs.
6. Defecate outdoors. With adult games, elimination is always assumed and never discussed. My kids, on the other hand, very deliberately relieved themselves in the bushes before entering the Tomb of Horrors, and discussed the logistics of keeping lookout before doing so.
5. Quietly remain hidden to allow a band of goblins to pass by unmolested. No opportunity for a fight is passed up by my friends.
4. Spend half their wealth having a dress altered from size Elf to size Halfling.
3. Attempt to converse with a gelatinous cube.
2. Google the elven language to learn a variety of phrases for the express purpose of insulting the dwarves in the party.
...and the top thing my kids do that my grown-up friends do not: