Yeah, that scans for me. It breaks up "getting ready...for a night out", but I think it works.

I think honestly it's just a reality that, if brevity is the soul of wit, then a punchy sentence needs to be compact and that means you need to get a bit funky with the grammar, so maybe the audience has to do a little work.

Maybe also "at which" is fine too, and I was just overthinking it.

One thing I won't bend on is that "to be starting to get ready" is objectively worse in every respect and is the main thing that throws people about the sentence.