I'm not really going to do what you asked as I don't want to "encourage" you to focus on the wrong thing! (I mean that in a less patronising way than that sounds!!). Yes some people do very well despite their ADHD and it is important to know that with the right support and medication outcomes can be very good. Medication for ADHD is the most effective "mental health" medication.
However it's even more important to not "bury one's head in the sand" focussing on positives and people who've done well despite their ADHD; outcomes for people with ADHD who aren't diagnosed, supported and/or medicated can be extremely poor: lower educational attainment, unable to hold down a job or relationship, lower life expectancy due to greater risk of accidents, risk taking behaviour, risk of addiction, poor health choices (eg unable to develop good habits/routines such as regular teeth brushing, regular exercise. and maintaining health related appts, greater risk of substance abuse, poor food choices), engaging in criminal behaviour (1 in 4 U.K. prisoners are thought to have ADHD), risk of Co-morbid conditions such as anxiety and depression.
But it's not all doom and gloom, as I said above treatment for ADHD is usually very effective and you are getting in there early in recognising it, but it's vital to follow through with exploring a diagnosis and getting the support/treatment he needs if he does have ADHD.
My DS was diagnosed in secondary school, lots of support was put in place and since then had done really well (before his diagnosis and support he wasn't coping at all). He's found a job with an incredibly flexible organisation that suits his ADHD and he's thriving.
PS I wouldn't assume any ADHD is mild from what you've said. He may just be inattentive rather than hyperactive. The symptoms can be less obvious but not necessarily mild, may all be going on inside his head rather than outside. Inattentive ADHD also becomes more obvious the more organisation is required and demands are placed. So for example in primary, a lot of organisation is done for you and there are few competing demands. This changes at secondary school when you have multiple classrooms, multiple teachers, homework to manage etc etc etc, and of course in adulthood when you are managing both your home and work life and everything gets much more complicated.
PPS this is really worth a watch:
Best of luck.