Do you find, Valmai, that if you do try to compete in volume with the melodeon, the extra pressure that you need to use makes the concertina sound flat?
Mine does, but it has been retuned since its 'Sally' days. It is more obvious when you play it to an electronic tuner.   I've been told that Salvationist instruments were tuned a fraction sharp because they were played loudly.

As I said, the baritone I handled was a beautiful instrument. I envy you yours.
Pip, however, wants to accompany himself. It may be years before he needs one to compete with other free-reeds, and unless he has a voice as deep as a bison, a tenor should be fine for him.   
I'm assuming Pip is for Philip.