Much like others have said, change passwords, remove charging cables etc…
With regard to their mess, put everything they’ve left lying around/their mess in a large /bin bucket (like the coloured rubbery ones from garden centres) and give a deadline for it to be cleared away, if not done then throw it all away (donate etc…) hide items of high value and regift them to them for good behaviour.
One thing you could consider is getting them to have a big clear out of their bedrooms and check they have enough storage.
Good luck I hope you find something that works.