It took me a while to figure out how to secure my double gate in the grass. My second gate is no longer screwed to a wooden stake in the ground.
After installing the cane bolt I realized having another pipe in the open position is the way to go.I have double gate too. It looks like we have the same solution.
For the "fixed" side, I simply pushed a 12" length of pvc pipe into the ground for the cane bolt. I have one in the closed, and one in the open position. It's worked great for 9 years.