Direct buried service wire from house to shop
Actual load is needed to calculate voltage drop, but at a full 240v 60A load #2 aluminum should be adequate to only experience 3% voltage drop, which is the maximum voltage drop recommended by the NEC for a feeder.
There is some small risk of load imbalance causing a larger voltage loss. If by chance you randomly more than 30A of loads to just one leg your voltage drop could exceed 3%.
You do need 4 wires, two hots, a neutral, and a separate ground for a 120/240v feeder.