They'll be fine. Sounds a little more like you're not handling it well, though, and projecting your feelings onto the kids. We had custody of our grandkids. The week of my granddaughter's 6th birthday, I told her to start thinking about what she wanted to do for her birthday because it would be her special day. The day of her birthday, before sunup, a light tap on my arm woke me. I opened my eyes to see this adorable little 6 year old, already dressed and wearing her orange cammo. She leaned in close and said, "Gramma, I know what I want to do for my birthday." So she and I went deer hunting. She saw me shoot the deer, watched me field dress it, asking a million questions, and helped me drag and load it into the back of the pickup. When we got home, Grampa came out and helped us hang it.
Later on I worried. Was that too much for her? Maybe letting her see a deer killed and gutted wasn't the brightest idea I'd ever had. I wasn't sure how to broach the subject without giving her the idea that she should have been upset. But during dinner that night, she was telling Grampa all about the hunt, the things we saw, how good the juniper smelled when we crushed the berries and rubbed them on us, and how good "her" deer was going to taste. Then she asked him when he was going to get the chance to get his deer, and could she go with him when he did? "I was really quiet, Grampa, and Gramma said I was a good 'looker'!"
I think how they react has a lot to do with how you handle it. That little girl is now 22, married, and would still jump in the truck with me on a moment's notice to go hunting.