How to tell my parents about older SO

Hi everyone.
Firstly, I apologize sincerely for the badly construed English, as I am Afrikaans.
I am in dire need of Constructive advice regarding the sensitive issue of (a) telling my parents about my older SO and (b) introducing everyone smoothly. In other words; I am trying to prepare for the worst beforehand; but in the meantime hoping, wishing and praying for the best.
But a bit of background information at first. I am about four months away from turning 21; as a working student I earn my own salary and live far from my extremely traditional family. Have seen them four times during this year in total; but speak to both my parents, as well as my brothers at least every second day. I ended my last relationship a long time ago due to my parents not agreeing and have refrained from dating since then, up until August. Trust as well as a lot of other factors definitely played the biggest part.
My SO and I met in February, but started dating at the end of August. I have met his whole, extended family and visit often. Everything seems to click and fall into place... Except for the fact that I have yet to tell my parents that we are seeing each other in a way other than 'friendship related.' 
Let me just clarify: my SO knew this (and all the reasons behind it) from the beginning.
I have not broached the dating subject with my family, due to my SO's age (he is 39, which makes me a total of 19 years younger) and fear of especially my father's extremely harsh judgement. My family is very traditional and I am trying my absolute best to plan exactly how to broach the subject maturely. Thus, in order to prove to them that he makes me happy and in essence, just try to gain my parents' initial tolerance and thereafter, hopefully, acceptance, is the goal. Ultimately, I don't want to have to distance myself from my family at all or hurt anyone by choosing.
My questions are as follows:
How would you recommend going about the talk with my parents?
What should I focus on to help build trust and tolerance maturely?
And as a parent; would you accept your daughter's choice if faced by a similiar situation arising? When it comes down to happiness and a conscientous relationship; where there is definitely no lack of respect and cameraderie.
Does the social norms we have in place generally make age differences of this range totally unacceptable and untolerable, even more so within the strict, traditional, patriarchial families? 
Any input would be greatly appreciated; even more so if you have experienced this dilemma firsthand.
Best regards.