Prompted by reading a thread on downsizing and de-cluttering.
I think it's reasonable to keep all their stuff while they are renting but as soon as they buy then I think they should take it.
Then it comes down to the sentimental things like teddies and toys.
I have kept a selection of good quality toys like lego and brio but I also have huge bags of teddies which I am now tempted to get rid of.