How do you do minimal with kids ?

[Milksheikha]

We are an expat family and at the moment have a big house where storage isn't an issue . Kids have absolutely heaving rooms with tat they have acquired over many moves and refuse to part with . They all are beyond toys and trinkets and mostly game or play sport ..actually mostly game.
We will more back to the UK soon and simply will not have room to store it.
They are not motivated to downsize or captivated by selling stuff for money.
In the past I had culls here and there but now they notice.

Can you give them a set amount of space/number of boxes they can bring with them and leave them to it? Anything that doesn't fit or doesn't get packed doesn't come.
My kids are much better at getting rid of things when they're going to friends or charity. Would that work??

Get rid of it when they are in school or at their dads. Is the honest answer.