Hi paulsmummy, Does your son have his own room? He could keep the marble run in there, tell him as it's his 'special' toy, he should keep it for himself. Just warn him of the dangers of putting things in his mouth (other than food). Does he tend to put things in his mouth at the moment? It's awful when they're so little and have to go through something so big. My eldest daughter has had a couple of ops, and has coped far better than I did! The hardest bit was having the anaesthetic (for me not her), but I held it together til she was sleeping.
Good Luck with it, will he have to wait long?