and can do pretty much whatever he wants to do”, it didn’t sound like he was having trouble staying active.
We all have to make adjustments as we age regarding what things we can do physically. I am in awe of twentysomethings who run up and down the subway stairs while texting, likely not even aware that hand railings exist. I can’t do that anymore. I used to be able to walk home from Manhattan to Brooklyn. I can’t do that anymore either. We all find new things we can do and find new ways to do things we used to do differently.
Since your dad is under the care of a cardiologist, his doctor has probably discussed with him what actIvities are safe for him. I’m pretty sure you should try to stop him from shoveling snow again.