I ended up the Aldi offer on 4x credit cards -
Chase 2x 7% $57.14 spend
WellsFargo 5% $60 spend
Amex 15% $40 spend

I purchased some groceries and a $25 Aldi gc on the Amex but bought gift cards only with the others.

It seems that Aldi only allows gc denominations in increments of $5, so
whereas I only needed $23.xx to hit $40 spend for the Amex offer, I could only buy a $20 gc or a $25 gc.