It's the only option you've got.
It saves you a great deal of money and you know you're a good driver so there's no harm in doing it or at least giving it a go to stop the nagging from a family member.
But how do you know you're doing it right? You only have the practical test to go on and by that time, you've spent your money not knowing if you're headed for a pass or fail.
Are you doing harm? There is a possibility you are to the extent the Government were considering making parent driving instruction illegal http://www.telegraph.co.uk/news/1922275/Parents-face-driving-lessons-ban.html. The 'jury' is still out on this although major changes are expected in forthcoming years.
You drive the way you've always driven and if you passed your driving test 20/30 years ago with no other driver training other than road experience and less than 30K miles per annum on your speedometer, then you may be doing more harm than good. The roads have changed, the driving skills needed to stay safe are much more than you ever learnt.
The main areas for concern passed on to new drivers by their parents are described here:
The Private Practice (DSA) Beginner's Control course will take place in the Instructor's car (with dual controls). The Private Practice Check-up and Mock will take place in the vehicle the new driver is learning in. Please see Your Car before proceeding with booking of the latter two courses.
Contact: 07767 886 839
(no obligation and you will be phoned back to save your phone bill)