Of course, I don’t recommend getting rid of the kids’ stuff without their permission, but you may be able to get them to go with one of these options (try using a prize for extra motivation):

Declutter: Once in a while, you as a parent can make your kids go through and get rid of anything they no longer love and enjoy. This is a great habit for anyone to learn. Give them a paper bag and have them fill it with stuff they no longer want. Then drop it off at the thrift store first chance you get.

Rebalance: Every time Christmas, a birthday, or any large gift-giving time rolls around, have the recipients get rid of the same number of items they just received.

Rotate: Divide the kids’ toys into 2 or 4 boxes. Label. Rotate the toys in (and the others out) every season (if you have 4 boxes) or every 6 months (if 2 boxes).

Pioneer Challenge: See if you can inspire and challenge your children to do this (or offer a fantastic prize). Challenge them to live like a pioneer child for a week, 2 weeks or a month. Have them choose their five favorite toys, and pack all the rest away. Keep the boxed toys out of reach and out of sight. Let your children discover life without a billion toys for a short period of time, and see what happens. If they are old enough, have them journal the experience. Maybe at the end of the time they’ll be willing to keep going, or get rid of a bunch more of their toys. This is a challenge Mom and Dad should try, too. You know which of your things are your “toys”. ;-)