If your children grew up happy and not speaking French is not an issue with them then you really are beating yourself up over nothing. They speak Welsh, which in North Wales is a real benefit.
I will go to my grave regretting taking the diagnosis of an opthalmic consultant about my son's eyesight problems without chasing up a second opinion straight away. By the time I did, as I felt he was not doing enough, quickly enough, it was discovered that my son had brain tumours that were destroying his optic nerves. Cancer treatment got rid of the tumours but left him partially sighted and with other health problems. He has never moaned about his problems, but could have had a bit better sight if I had been less trusting of the consultant and not wasted two months.
But I do sort-of-regret not taking ballet lessons when I was 12. A friend asked me if I was interested. As a football playing rufty-tufty lad, that was a quick and easy decision. I've always wondered if I was too hasty.
I have no major regrets, I suppose my only minor regret was not following through with sport. I was a reasonably good football player, and fairly good club cyclist, although my results might suggest otherwise. I went to work at 16 and although I kept up the sports, I didn't give enough time to training.