Your horses are super cute, and I'm not trying to be critical of you. I just don't want you to be hurt, so please listen to what me and the others are saying. I don't think you truly understand just how fast horses can pull back. There's usually no warning, and I guarantee you cannot react fast enough to pull the end of the rope to do your "quick release". It just isn't going to happen. As someone who has a horse who is a chronic puller (might go months without anything and then boom, it happens randomly), I'm always super careful about how I tie her and where I tie her, and even then we still sometimes run into problems. She's pulled back so hard and so fast (with a quick release knot) that it ended up melting the rope together and I had to cut it off the post (at least it was a solid post so she didn't drag it after herself) to free her. Tying your rope to twine is an excellent recommendation and I need to employ that more often while tying my own horses. I cannot reiterate this enough: You cannot react fast enough to release that knot. You just can't. Horses win every time in that regard.