Procrastination for the win!
Because I was lazy, the hairpin legs I wanted were $20 less per four-pack ($49.99 vs. $69.99) on Amazon.
I bought them and we bought screws at OSH, and now, ta-da!
I still need to put vanish on them, but at least we have alternate seating for the next chair break. I have varnish in the garage, so I just need to dig it out. I also need to figure out some solution to protect our wood floors. Considering wrapping the bottom of the legs with yarn.
The grand total is (rounded up) $115 for two benches.