Would you mulch this whole area, or just mulch on the right side of the line I drew in the picture?

I guess I’ll start by explaining what I’m doing. I initially started laying out this area to install pavers. In-laws wanted a paver walkway to the sidewalk from the front door. Problem is it drops off very sharp before the sidewalk so I said I’d add some stairs at the end of the walkway to the sidewalk. (Wish I would’ve built the stairs first but whatever, I laid it out exactly where it will be going) But as I’m prepping for the pavers I realize how badly sloped the hill is going from the walkway to the driveway. I was worried about erosion and the corner giving out. So I had to add a retaining wall. Turned into a huge job I’m doing for free and by myself lol ugh I’m an electrician not a hardscaper. But anyway, what would you guys do for this section I backfilled?