Well maybe you should try what I used to call "toy sort", it is for kids under 10.
You dump EVERYTHING into the middle of the room (toy-wise). Start with a trash bag and toss broken stuff. Find a big box and collect a box of "baby" toys your kids have outgrown, to donate to charity or a friend with a younger kid. They love telling you which toys are too babyish. Then put everything left back into its sets and kits and boxes and whatever. Things with parts missing get tossed. I make the kids do a lot of this work, especially when it comes to finding and putting the toy parts back together. If you take each toy set one at a time it is more fun. "Lets find everything that has wheels" or "lets find all the lego next"....Then take what is LEFT of the reassembed and resorted toys and divide it into two.....and put 1/2 away on your shelves or toy storage and the other half in a big bin from Wallmart, or a giant cardboard box. Put this second box in the garage. I would put entire kits of toys away, not half of each type.
Then, on some day that they are bored and driving you crazy, have them box up those toys they have been using and exchange it for the ones in the box. You would be surprised how fun those toys are to them again.
I used this to great success. They don't really need all those toys and sometimes there is an overload/overstimulation when there are too many toys. And one time when our neighbors had a fire, I just took the garage box over to their house and gave it to them.
I was a girl scout leader and a cub scout den mother so I do have a few tricks up my sleeve, they just are not usually about self-sufficiency, but try that Java, it really works.