Yeah, sounds like the women was given a litter of kittens with long fur and then was giving them away, labelling them as maine coons in the hopes that they would go faster (so long as she wasn't a byb trying to charge a couple hundred dollars for the kittens, I don't see anything overly wrong with that). I mean, I wouldn't call that the most defining coon characteristic, I'd go with the unusual size, feather duster tails, tufted ears, and I believe tufted toes as well.
And as far as older line bengal goes, never heard of that term before, seems a little strange to me. If I were to think of very first/original bengal I'd think of F1's, F2's and early generation Bengals with very recent ALC history, not like most bengals you see today.
I really don't think they have any purebred in them (with the exception of Apple where there is the possibility just from her head and body shape). That is one area where cats and dogs really differ, while most mixed dogs are the mixture of various, usually mostly discernible pure breds, it is the exact opposite for cats, most purebreds are the result of mixing mixed cats with similar traits, meaning all of those traits in purebreds can be found in the regular population, so most cats have nothing in them, but we love them all the same.
Either way, you probably will never know for 100% sure, but you can be certain that you have three very gorgeous kitties.