I got my 7-to-11 children into D&D in the following way:
1)
Fully pregenerated characters stats, while the non-stats (e.g. name and description) are added by the children themselves: in other words,
all the crunch is on me, all the fluff is on them. This removes the needs for understanding any rule and spend time filling a character sheet before starting to play, without removing the concept of character creation entirely. Then, as soon as they levelled up to 2nd level, they got to also make crunch choices, but by that time they had already played a few times.
I needed a trick with races: I wanted them to choose race as part of designing their characters identity, but I still wanted the stats to be pregenerated and ready to use, so all the pregenerated characters used Human stats, and race was demoted to a cosmetic choice only.
2)
Simplified character sheets:
http://www.enworld.org/forum/rpgdownloads.php?do=download&downloadid=1415
I wanted the character sheet to have less stuff but more open space, so I removed anything that was non-essential, duplicate, or temporary.
3)
No rules explanation until a rule needs to be used. This allows to start playing the game very quickly. The only thing I explained was the role of each character class (only 5 of them were used in the pregens) in the world, so that they could choose the pregen they liked most.
4)
Gradual introduction of complications. The first adventure was short (1 session), with straightforward plot, and TotM combat encounters against 1-2 monsters at a time. Then I introduced the idea of investing treasure in upgraded equipment. With the second adventure, they got more freedom in choosing what to do. Then a combat against one monster per PC. Then a more complicated combat with terrain features, which prompted us to start using minis (but no grid, thanks!)... Trying to add ONE complication at a time and its required rules helps a lot. It could be cover, darkness, flying monsters, stealth, etc.
5) Have some
gadget, novelty or multimedia boost added to the game every few sessions if you feel they are getting tired a bit. In their first session it was the character sheet and polyhedral dice, something they've never seen before in other games they played and they were immediately interested into. The character sheet was later expanded with a page for treasure/equipment, and another page with more room for character description, history and social connections, as they grew with the story. Then we added Lego minis, followed up with more Lego bricks constructions to represent obstacles and terrain features. Then we added appropriate music in the background, to change the mood with the adventure scenes. Now we start using action cards to better visualize/remember which spells or abilities they can use, and using what action type. Kids seem to love every new idea being used to expand their gaming experience!