Lattice Foundation - Concrete Piles or Wall

I've got a backyard deck which is in good condition, which we enclosed a couple of years ago with conventional lattice panels. This has held up very well, especially since I had the foresight to anchor the bottom of the panels into a lateral notch that I cut into a series of pressure treated garden edging timbers that run horizontally along the bottom of the installation.

When we enclosed this deck I also remembered to bury a drainage pipe, to pull away the water that would accumulate under the deck when it rains. That's worked pretty well also, although recently I've noted some gradual erosion of the soil foundation under the garden timbers - to point where the timbers and lattice have begun to pull away from their original position.



With that foundational background (okay, some pun intended . . .), my intent was to fix this through either one of two approaches. Excavate and put in three or four concrete form tubes, to the original level of the garden timbers, and then set the timbers back resting on these new "piles" when the concrete cures. The other alternative would be to actually lay down a very shallow, and continuous mini-foundation, and then re-set the garden timbers. I'm leaning toward the concrete "pile" approach, since it will easier, will still allow better surface water drainage from under the deck, and won't require quite as much digging and "engineering" - in forming and pouring a miniature foundation. And since none of these timbers, nor the lattice it notches into very heavy (or load bearing), my guess is these "piles" can be set pretty shallow, but certainly no deeper than maybe 24-30"? I'm certain that someone will suggest the possibility of frost/freezing and heaving, but is that really a source of concern for something as simple as this (I'm willing to be told it is . . . )? What are people thinking about this?