Raising 9 kids, and camping a lot, I have always allowed them to help with the campfires. Some people over the years think I was wrong...however...none have ever got burnt and allow my grandkids to also help when camping. (your thoughts?)
I think it's fine. I let my kids help as long as we are right there to ensure they are doing things safely - why not? Obviously I don't let the younger ones actually light the fire, but my oldest has helped with that since he was 12. It's fun and it teaches them respect for nature and also how to be safe. Fire building is a good skill to have.
I usually started the younger kids with "collecting" kindling...and then, to collecting larger firewood...we created different piles throughout the day in anticipation of the evening fire...I liked to pair the younger kids with teenagers...
Yes, we often let the kids prepare it, look for the logs, put it together. Of course, always with an adult with them. It is fun for them and the pride of doing something which everyone enjoys always give them the feeling of satisfaction.
Growing up on a lake there were always campfires. Kids were always good for finding the wood. As we got older it moved to building then lighting. Now as the parent I get to run my kids through the same path of making campfires.
I think it's fine as well. You're teaching them how to build a fire and how to be respectful and responsible with fire. It's a win-win situation. As far as I'm concerned there's nothing better than sitting around a campfire with people that you love to be with!!!!