I know various e-readers have the ability to look up unfamiliar words or phrases in a dictionary by tapping on them, so you can focus on only looking up things that you don't know, or look for another definition for some word if the definition you have doesn't quite fit. For instance, I would probably need to revisit my parse in that first sentence, "Arion, since he (or perhaps some unspecified deed? but why not the ablative absolute here?) was accomplished abroad, ..." using proficio as "has been accomplished" instead of proficiscor for "departed"); looking up profectus in a dictionary would yield the other base word.
I also wonder about jotting down translation notes while reading -- when seriously trying to translate a text, writing down notes in the margins or between lines (if there's appropriate spacing) helps a ton. At least until you're familiar with the grammar and the constructions, laboring through the translation is a huge help.
For someone like me who is reasonably familiar with the grammar, but might be rusty on the actual vocabulary (having last needed to use it in any semi-serious context more than a decade ago), I could see myself referring to the existing app's translation on occasion to give me some ideas regarding the actual words. But I don't know how helpful it is for someone newer to the language, who'd need more than just vocab.
Another commenter also mentions the possibility of pairing the Latin text with a well-established English translation. That might also be interesting; I could certainly muddle my way through a translation without knowing the grammar, but I would make plenty of mistakes if I didn't stop to think about cases and verb forms. What I think would help most is to perform a surface reading, followed by a refinement to make the text more idiomatic.
For instance, taking one of the sentences in the second paragraph: "Pecunia omni nautis oblata, vitam deprecatus est." My surface reading would look something like... "With all money offered to sailors, he begged his life." I might then refine that to "Having offered the sailors all of his money, he begged for his life."