Hoviss00:
You'd have done better to start a new thread, rather than to post on Leelo's one, as things could get rather confusing!
However you still deserve an answer:
The are two separate laws. One refers to 'offensive weapons' and the other refers to 'bladed articles'. If the prosecution pursue a case under the 'bladed article' law, and they can establish that your son was definitely carrying a sword, then the chances of a prison sentence are quite high. (If they can establish that he was carrying the sword in relation to some ongoing 'aggro' in the town, he'll almost certainly go to prison).
However if the charge only relates to an 'offensive weapon', and the prosecution are unable to establish that it was a bladed item, the chance of a custodial sentence will be much lower. It's carrying knives (and similar articles), particularly when it might appear that the offender is seeking a victim, that generally leads to the most serious sentences.
I'm sorry that my answer is a bit vague but, without knowing the exact details of the prosecution's case, it's impossible to be more specific.
Chris