Leg cramps in children at night?

In the recent 2 weeks, my elder boy Joel (7 years old) woke up on two different nights, crying of leg cramps. This puzzled me, as on the two occasions he had not been doing any extreme sports. As usual I started googling and reading up for possible causes.

Possible causes of leg cramps in children are as such:

1. Over exertion during some high intensity activities or activities that is new to the child may potentially trigger cramps, especially so if no proper warm up and stretching has been done. 
2. Dehydration. As body fluid helps transport minerals that faclitiate and regulates body function, if  water is not sufficiently replenished after excessive perspiration, body electrolyte will be off balanced (This will be explained in point 3) , as well as irregular body temperature. Subsequently, impacting muscle responses as well.
3. Deficiency in certain minerals (Calcium, magnesium, potassium and sodium). Minerals as listed are active for transmiting messages within our body (The Electrolytes), as well as playing critical roles with our cellular function. Defficiency in any of these minerals will off balance the electrolytes, and  the signal systems within our body will be affected. As a result, leg cramps may suffices.
4. Flat foot or leg aligntment issue may also be another possible cause of leg cramps due to the uneven distribution of work loads done on the compensating leg muscles.
5. Last possible cause, which I hope most to be the reason, is that rapid growth could also possibly trigger leg cramps. This is due to the rapid growth in the bones and skeletal structure would also require muscles to adjust and grow accordingly. However, cramps can sometimes occurr as the body is in the adjustment process.

Having gone through the possible causes, I would be more careful and adopt measures that could help avoid the situation. Such as ensuring proper warm up and stretching is being done before and after exercises or strenuous activities.

Lastly, as Joel has always been a fussy eater, I would have to ensure more potassium and magnesium rich food, such as citrus fruits or tropical fruits (Especially bananas, honeydews, oranges or prunes ) be provided daily. As well as other minerals rich food such as nuts (Even peanut butter is good source) and vegetables (Green leafy vegetables and potatoes) be included in his daily diet. 

It's definitely a long learning process being a mummy!