No way to run a 3,500 watt generator and a corded jackhammer (probably rent it)?
I have REALLY rocky soil here, seems like more rocks than dirt and one thing I learned is that breaking up rocks is a lot more difficult than concrete especially since the dirt absorbs and dissipates some of the energy from the hammer. Bigger is better in this case, and that's why I'd use an 1-1/8" electric jackhammer, not an SDS max or especially SDS plus hammer. Doubly so if they were cordless tools, probably run those batteries down in hurry. At least with electric it keeps going (and fueling a generator is easy).
I have the one pictured and couldn't break a rock that was a little bigger than a basketball. I resorted to using my SDS plus rotary hammer and drilling a bunch of holes were it was exposed and in the way, then using the SDS max hammer to break off what I could.