That is plausible.I've been trying to figure out how the dehydrator came up in conversation ,with the children, while their grandparents are deathly ill.
I keep thinking that the family would have been discussing the possible source of the illness with the doctors at that time. The family would be asked about what was eaten, etc.
Here is ONE possibility that comes to mind:
A poison expert is asking the family about possible food poisoning and asks about mushrooms. The kids say " Mom, weren't you drying mushrooms in the dehydrator ?"
Dad jumps in with his accusation and Mom panics and dumps it? [unless sweet already dumped it]
Dependent on the timeframe of the dehydrator being dumped (I take EP’s word for it with a grain of salt - I will rely on cctv when it’s revealed), I had also surmised that she may have had the dehydrator in the car with her when kids when she took them to the movies on the Saturday (or had mentioned to them that she had gone to the tip or something). In my mind this would give give rise to the kids knowing about the dehydrator and potentially for it coming up in the conversation.