This is an observation not a criticism, DA. Something just does not ring true for me, who is not particularly concerned nor unconcerned with organic practices, with buying organic compost in plastic bags.
The football field I did in August took 3 dump trucks. In bags, it would have been 30 pallets and 1,200 (!) plastic bags to dispose of. Granted it made more sense to use bulk with all that in one location but the accumulated waste will be the same for you if you topdress 57M, more or less, at a medium rate on several widespread lawns. I understand your concerns and reluctance.
Cost may be a bigger factor than you realize. Think of yourself if you don't think the customer will mind the difference. On the football field the compost cost me $552 plus tax and delivery. In bags at $4 (I have no idea) it would have been $4,800 plus tax and delivery - on a job I did I one long afternoon. So even if the customer had ponied up at the higher rate, I would have gone home with $4,200 more than you. Of course I did not charge them as though I had paid $4/bag but I think there is something useful in the story, some apparent opportunity in that difference for you and the customer both.
You're a good guy here on lawnsite. I've never seen you complain something was too difficult. I know if you get into this you will do a good job, get good results, and not find it overly difficult. I believe you will find it rewarding and that performing the service well will further differentiate your business.