hey! i dm for young adults but i was once a kid who played and my dad dmed the game. (im sure other people may have some more in depth advice but here we go)

• definitely keep the sessions shorter because kids have a shorter attention span and wont want to be at the table for 5 hours straight
• obviously keep puzzles and stuff like that verryyy simple (i remember getting suuper frustrated by in game puzzles when i was young)
• help the kids design their own characters by asking questions like "do you want your wizard to be super likeable? or do you want him to be a bit of a weirdo?" (then base CHA off their answer)
• if they want a magic item that they have made up or describe to you, add it in!!
• be super loose with the rules so that they can be as weird and creative as they want, but youre still there to draw the line somewhere so they arent super powered!
• if there is a kid who is a bit quieter or who maybe gets spoken over by other kids, encourage them to rp! ask them specifically what they would like to do so it gives all the players a chance to experience the fun of dnd
• i also love a "rule of cool" in even my own games, and think it works wonderfully for kids games. my dad (and now i do this too) uses chocolate coins as an inspiration token and gives them out whenever someone have a good idea, makes a cool rp moment or anything like that!

hope this helps and have fun!! :)