I'd look for an old used aluminum framed revolver. Most of the department store guns would be great and were made (mostly) by reputable companies. I've got an old JC Higgins that is a lot of fun. Also I have an old "Western Automotive" made by High Standard. Neither cost over $100.
We did that trip when my kids were that age (no teenager). Had a great time, though we never went to Cody. Hit Devil's Tower on the way out, cruised around the bighorns for a couple days. On the way back we camped out and shot prairie dogs, hit the Black Hills, saw Rushmore (from a distance)...
Shit happens and everyone makes mistakes. No one was hurt and nothing was damaged. Shrug it off and move on.
My dad was coming up on a canoe once, he didn't see it/wasn't paying attention. Us kids warned him and he swerved off and apologized. Not much more you can do.
Years ago I shot a doe whitetail that I never recovered. She was about 10 yards when I shot and I was on the ground, level with her. Shot looked perfect and she flinched at the hit and continued on her way. She joined a few other does in the field in front of me and I kept waiting for her to...