Virgil, like any writer, has a set of diction, a manner of style and a set frame of writing. I believe that by slowly and comfortably translating his shorter works I will be well-prepared for the “mountain” of the “Aeneid”.
I wonder how helpful reading the eclogues and georgics would be? The eclogues for example engage directly with Theocritus and a whole tradition of Hellenistic poetry. Understanding them is a completely different proposal than understanding the Aeneid. The poetic diction and mode of expression is rather different.
The notion of “ascent” from eclogues to epic is something that we have imposed on the simple historical fact there is a chronology to Vergil’s works. Rather than suspecting some kind of artistic programme or “development”, might it not be more plausible that there were simply financial reasons that his first work was short. The Aeneid took him some time to write (and in fact he didnt really complete it - whether epic is “completable” is another issue) and presumably he didnt want to wait years before he published anything at all.
Pastoral, didactic and epic poetry are separate genres and they have their own conventions. I find the eclogues much more difficult to read than the Aeneid.
Rather than waste time with a lot of preparation why dont you just start reading the Aeneid if that’s your ambition. In previous discussions on the forum MWH who knows what he is talking about suggests that maybe Ovid’s Metamorphosis is a better preparation for the Aeneid. Thats worth thinking about.
Reading part of the Aeneid is entirely a respectable thing to do especially at first. Most people unless they have a professional interest dont read the whole of the Aeneid these days. Historically the last books (the “Iliad”) were much less read.
“Reading Virgil Aeneid I and II” by Peter Jones, CUP, 2011 would be an excellent introduction to the Aeneid.
“This book follows the same pattern as my Reading Ovid (Cambridge University Press 2007). It assumes readers have done a year of Latin and have a grasp of basic grammar and vocabulary at about the level of Reading Latin (Jones and Sidwell, Cambridge University Press 1986) or Wheelock’s Latin (New York 2000). Line-by-line help with grammar and vocabulary is generous to start with, and regular learning vocabularies specify what must now be learned because it will not feature in the glossing again (though the total vocabulary set to be learned is contained at the back, pp. 302–15).”
Jones also says:
"Virgil is not easy. The text, therefore, is split into quite small passages to start with to encourage careful reading, gradually extending in length. "
Be warned. 
But if you are serious about having a sound basis to work from after Wheelock I would suggest a prose author like Caesar or Cicero. Or read some prose alongside Vergil or Ovid.
Finally, there have been endless debates here about translation. You need to have a thorough understanding of Latin to be able to start to think about a translation. Making a good translation requires skills beyond understanding the Latin. Not all (most?) of us have those skills or are prepared to spend the necessary time to develop them. Historically “good” translations have been produced by accomplished poets. They usually have something to tell us about the text. Think of Dryden. What relation their translations have to Vergil is a complex question. That said it’s possible to improve our translations a bit but matching Virgil’s poetic genius is a tall order for anyone.
How you use your time is up to you. I dont want to sound to discouraging but I think the mountain you face is not just the length of the Aeneid or the complexity of the syntax, but many difficulties I am not sure are apparent to you. Like Dante you definitely need a guide (mountains and purgatory brought that image to mind
)