I'll say something like this to them:
I've got a problem; I'm on one side of the river and all my toys are on the other. I want to get to my toys ... but the only thing I've got to help me is food.It's always food.
And then it's on them to come up with suggestions. Answers to that one included:
- make a raft out of breadsticks glued together with Nutella
- throw bread into the river until it absorbs all of the water
- make a dam out of sausages
- use half an Easter egg as a ladle to empty the river
- throw piles of chocolate into the river and use them as stepping stones
We've established a few conventions as we've played, for example it's not allowed to use containers in the solutions - so a chair made out of tins of baked beans was rejected in one game. We've also built up some solution libraries - so if a sheet of material is required it's taken as read that it can be knitted out of spaghetti using, say, celery as needles.
Plausibility is important but not fundamental - so, a breadstick raft seems to be acceptable because it could in principle float even if in practice using chocolate spread as adhesive is impractical. Out-and-out fantasy - such as making a helicopter out of butter - is always shouted down.
Sometimes I'll provoke things by offering a new perspective such as getting a cow to swim across the river and riding on its back. And then we're onto questions: Is a cow food? Is a live cow food? Is a cow a container of food?
I really love this stuff. (And thankfully, at the moment, so do they.)