Fat bike cargo rack, primary use - dragging kids on a sled - OR tie it to the saddle (sitting on a dropper post)?

I want to buy a cargo rack for my fat bike to drag kids behind me on a sled this winter. Last year I tied the sled directly to my seat (non dropper post) and it worked perfectly fine. This year I want to get a dropper post, but im not sure if it's OK to pull on the dropper post that way, dragging the kids around in snow - so I'm looking at very simple but sturdy cargo racks that I can tie a sled to.