I think it has to be the oral history. Hands down.
I've read versions of those horror stories, they're fun and probably easy to write, but the one that is going to cry out to be written is the pioneer history and related stories.
Working on that romance, you'll wonder why you didn't buckle down and write the family stories. The romances are a dime a dozen, Harlequin and Silhouette crank them out every month. Someone gets paid a few thousand dollars then uses the formula again and again. If you write enough of them you might break out of the Harlequin stable and publish them in mainstream publishers, but they actually aren't that easy to market.
The oral history is something that you might well interest a local press in, or a university press. No income to speak of, but you would publish it.