So I've ordered my DnD stuff and look forward to its arrival next week. And I've gotten parental approval from the nephew's mom, who also was interested in playing. So we're on track for a fun party-of-three adventure (I'll play a third party member, largely as a henchman). My wife is thus far completely uninterested, but that means she can watch our kids during the games. :)
I'm going to start with the Starter Set adventures, as that will help them roll up a first character and learn the most basic game mechanics. It will also give us a basic adventure to help me learn the ropes of a DM. After that, however, I'm getting interested in designing my own adventure.
Or an adaptation of an adventure. While I have an old module idea that I eventually would love to try in pen and paper, it would be fairly involved and perhaps too mature for an 8-year old. So I'm thinking that our first several adventures might be adaptations of NWN modules. Snickersnack!, which I just finished the other night, could be a great opening module, assuming I can recreate the humor of the kobolds (and find a more level-appropriate quest reward). It's simple, short, and fun. And Cave of Songs is another that might translate very well: powerful ideas, but very little required long dialog and a lot of stuff that could be cut or embellished as needed.
I'm getting ahead of myself a bit here--they may try this and hate it--but this should be fun. DMing will no doubt require preparation, but I'd guess the hours requirement is at least an order of magnitude lower than creating an effective NWN module.
Now if only my books would arrive quickly. I'm looking forward to learning the 4th edition rules. I'll roll up one each of a fighter, rogue, wizard, and cleric, so I can choose a character to complement my players' choices.