This is a great question especially considering there are so many people using Genki alongside WaniKani. I am in a slightly different situation as I completed Genki 1 & 2 in a formal Japanese class and only later joined WaniKani to start taking Kanji more seriously, but you might find my experience helpful as you plan your study road map.
In general, I found that Genki should primarily be used as a grammar series rather than a vocabulary series. In both Genki 1 & 2, most of the vocabulary words are there just to compose the example dialog. The consequence for the student is that it feels like there are just a random mish-mosh of unrelated words thrown into a list. In Genki 1, there are some important adjective and verb lists as well as functional language vocabulary lists at the end of a chapter (i.e. “At the Train Station”), but those sort of disappear in Genki 2.
I agree with the other people here that focusing on grammar and basic vocabulary would be best idea to start. WaniKani is light years ahead of the Kanji reference at the back of the books, so continue here as soon as you can start to compose beginner-level sentences. My recommendation is to get comfortable up until the te-form and short form in the middle of Genki 1. Then you’ll be in solid shape to compliment Genki with WaniKani without feeling overloaded. I’m currently reviewing the Genki series and WaniKani shooting for the N4 JLPT (or higher if I have time!).