Would you get Main Cabin Extra in AA Economy? If so, I would likely choose that, unless you can secure some sort of other extended legroom seat on QR (or AY, I guess). If flying AY, I would break up the trip with a day in HEL… two consecutive 9 hr segments in coach would be hell for me.

How likely do you think is it that you are actually going to get all the J seats you are looking for for your family trip later on? Would be awful to give up the bird in the hand (QR J). Just saying.