Are they being exposed to marijuana? Can cause a vomiting illness syndrome. Reason kids are more affected is because their bodies are smaller and toxic load is bigger in smaller bodies.

Are they getting enough sodium? Also sounds like a salt deficiency. Gatorade helps and watermelon with salt on it.

Are your gas bills high compared to neighbors? That indicates a leak.

I would say eat bananas for radiation but it sounds to me like they could already possibly be overdosing on potassium from the sodium deficiency.