Rana I too have an Lachenal English concertina, a 56 button Excelcior circa 1875 with a beautiful tone. All I would say is don't wait until your knees start to give out morris dancing - maybe they never will! I dance too but I started to learn to play about 11 months ago - completely from scratch, with little help and never before having been able to read music. But I do practice virtually every day.
Of course, it is frustrating at first! I initially started with the Frank Butler tutor book but I found it too boring - so I started to learn a few tunes which I knew from the dots and I can now play unaided some 30 tunes (not always perfectly though) and am in various stages of learning some 50 others. Although I still have a long way to go, particularly in terms of playing with other people, it is such a joy!
Start NOW !

"Oh Shanendoah, I long to hear you ...!"
Alan