The jails are full, unlike Paris Hilton, this crime only had an economic impact, jail won't help protect anyone and won't deter people who think they are cleverer than HMRC... How about the judge offering the son a deal - he gets his dad to give up all his wealth and resign from government; the son also giving up all his wealth. All audited. The money can then be used to build a prison.
The muppet of a son was most probably trying to impress his dad by generating wealth but his dad is being a idiot in still insisting his son has done nothing wrong. Cue expensive QC being hired to quash the conviction on appeal because of some technicality...