I will say to the captains and managers before friendlies that I will try to manage things, but I can't manage the unmanageable. Things like VC, obvious cases of SFP, OFFINABUS, etc, will still see cards come out friendly or not.
For friendlies in England at step 5 and above, so supply league, the FA mandate the level of referee required. As an example, a supply league team against a contrib team could be refereed by a L4, but if it was supply league against National League North or South it would have to be at least a L3. There is a matrix for this on page 5 of the link below.
http://sportdocbox.com/World_Soccer...-non-competition-matches-policy-document.html
They also mandate the fees for these games, and they are now fee only with no expenses. These can be seen on page 4 of the same document.