Choice of narrative

Thanks to my unique proximity to the parties involved, I have compiled a good deal of documentation regarding the road trip. My mother saved all the letters my father sent her while on the road (they weren't married then, only dating), and my father saved a decent amount of memorabilia and photos in a scrapbook. That, in addition to his recollections, anecdotes, and personal chronological narrative, albeit it over 50 years after the fact, make for a bountiful pail of information to draw from.
However, there is no substitute for traveling the trodden route. I have no firsthand experience of the roads they rode down, the people they met (nine countries were stepped on), and realistically only a rudimentary understanding of most of the cultures they mixed with. That is why I believe I can only approach the writing of this book as more of a character study than a road trip. In other words, the plot would be driven by the main character's development while on the road, as opposed to focusing on the trip itself and writing it as an adventure novel. My dilemma is whether to write it as a first or third person narrative. If done as a first person account, I'm also considering including a second narrator, also in the first person, which would be the love interest back home. I think it would be interesting to have the tale peppered with stories and perspectives of everyday life through the eyes a young, single socialite in a thriving cosmopolitan city while her beau is away.
Not sure. I need to develop both ideas a little further before deciding which way to go.