Yes 2A is more than sufficient — OpenSprinkler Latch consumes well under 1A so 2A is plenty.
You may want to check if you can find LM2596 modules like the one in the Amazon link. These are widely available and much cheaper than the popolu module. Also they are available on Aliexpress — the shipping can be long during COVID, but the price is unbeatable on Aliexpress.
OpenSprinkler Latch can work with 7.5V input voltage — it has built-in boost converter to generate enough voltage to drive latching valves. So even if input voltage is down to 5V, it can still drive latching solenoids.