Hate to point this out but you can only get a police caution if you admit that you're guilty of the offence. If they weren't guilty, why were you friends admitting they were?
What's so different between pleading your case in front of magistrates (non-legally qualified members of the public) as opposed to a jury (non-legally qualified members of the public) other than the number (3 magistrates as opposed to 12 jurors)? After all, according to you, jurors always believe the person making the accusation in any event so it's not going to make any difference is it?
Arrests may appear on someone's 'criminal record' but only if you mean by that an enhanced CRB check and, typically, they would only appear if relevant to the nature of the check. For example, you might have been arrested on child pornography offences and be awaiting a charging decision by the CPS when you apply for a job working with children. What would be the problem with the fact that you'd been arrested for child pornography offences being disclosed to your potential employer? Arrests do not appear on PNC printouts but warnings, final warnings, and cautions do.