I DM for a group of 9 and 10 year olds (and one other dad). The biggest problems:
they have no D&D context like us long time players, so they forget to do obvious things, like search the bodies and take the loot.
it is very difficult to get that many people together timing wise, so they forget rules and the basics of the game.
I roll behind the screen, I don't need character deaths just yet (only in their 2nd/3rd dungeon).
You need constant action, I don't even bother with much role play, they get plenty of that playing with our minis and their legos when they polay on their own.
Spells and special abilities are almost impossible for them to remember, especially buff spells. I'll be using my combat pad (great tool) to track that for/with them.
There is an old Dungeon magazine with an adventure entitled fountain of health. It is easy to update/add more encounters, and comes with a large map of a ruined shrine. I highly recommend it (I added an ettercap and lots and lots of spiders).
Minis and maps are almost a must.
edit: let me know if anyone wants me to post on how things are going/suggestions. Right now they are going through the sunless citadel (the kids wanted to talk to Meepo, the adult playing the chaotic barbarian wanted to kill him, the kids talked him into not killing. The youngest child drank the "dragon breath" potion, and then promptly forgot about it in the next encounter, one I had made much more difficult by adding a spellcasting goblin {the youngest plays a nearly 3rd level fighter based on Regdar - the other players chant "cleave, cleave, cleave" as he attacks puny guys like goblins}).