ADHD makes it incredibly hard to think from someone else's point of view
This post resonated a lot with my own parental challenges.
First, i've found that ADHD and balance issues are comorbid. I've seen this be a recurring theme in a couple of support groups i've been part of. A therapist i've seen said balance issues are common in a lot of people who don't have a strong idea of a self for various reasons, and there are therapies that are designed to improve your sense of what is your body and what isn't, or where your body ends and the rest of the world begins. It's apparently very useful and goes a long way in healing the mind. Some people I've known have tried improving their balance issues by learning to use a skateboard and they say it has helped their mind.
Secondly. I had postpartum depression and some of what you mention are things I struggled with and beat myself up about. I had more anxiety about my kid falling over and less faith in her abilities; hence, I was not as much of a fun parent. I know what you're talking about. I'd suggest a different way to look at it. As a parent, you're responsible for your child's safety. You aren't very confident in your abilities to do complex maneuvers with your daughter in tow. It could be for whatever reason. You're just being responsible when you refuse to jump over tricky rocks with your kid. Especially since one parent is already out of commission with a hurt ankle. Not every parent has to be good at everything. When I go to the park, many parents don't let their kids play in the water because they think their kids will catch cold, etc. Some parents don't even let their kids play with chalk because they don't want to deal with the laundry. Think back to your own childhood, your parents might have said no to so many things because they weren't prepared to deal with it. That's perfectly okay as a parent.
But also I don't think a lack of 'empathy' leads you to find this difficult. In some convoluted way, maybe. It's mostly just not paying attention to the other person's cues (which happens for various reasons). But also, if it's a new situation for you, you're going to find it difficult anyway. In outdoorsy groups I'm part of, there's always someone or the other who aren't confident enough to help others even if they are decent at it. If you do things like this a handful of times in a safe environment, you'll figure out what cues to watch for and become better at it.
That's basically what I had to do. watch my husband supervise our child on dangerous things, then supervise while he's around, and then finally just do it myself.