Sounds like my girls and they are only 7!
They do basic things around the house.....pick up all toys at the end of the day, put dirty laundry in the laundry room, put dirty dishes in the sink, etc.
Their rooms are atrocious also because my MIL bombards them with gifts for every holiday (even St. Patty's Day!). When I say bombard, I mean like 5-6 giant (like the 3 foot tall) gift bags full of CRAP. They are total packrats too.
Anyway.....sorry for the rant.....
I used to declutter their rooms when they were away from the house, but they would get upset to find some things missing.
The last declutter time, I asked if they wanted me to do it or if they wanted to do it.
They both wanted me to do it. It is WAY too overwhelming for them. I mean, how could it not be? It was very overwhelming for me too!
I told them that if I did it, they couldn't complain about what was gone. They agreed, but they did make small requests, like "don't get rid of any Peanuts stuff" & "don't get rid of neopets", etc. I respected those wishes.
They weren't allowed in their rooms while I was doing it, but if they did happen to see something that I was getting rid of and they really wanted to keep, I made them pick out 2 things to get rid of in place of it.
I donated tons of stuff! Their rooms are now cleaner and easier to KEEP clean. Now they can do it themselves (until the next holiday

).
I was worried about doing it for them too, but then I see how overwhelming it can be to a kid.
Oh, and if they had said that they wanted to declutter their own rooms, I was going to give them 3-4 (maybe more) empty bags or boxes that they had to fill.
Hope that helps a little. Mine do the eye-rolling too. Drives me nuts! And if they slam a door, I make them re-shut it nicely. They don't slam doors anymore....well, until they are teenagers, I'm sure.
