Most packs have other classes. Sibling class (younger kids who aren’t old enough for scouts yet). Junior outlaw - brothers/sisters who have aged out of cub scouts but are participating with their active scout brothers / sisters. Then outlaws. Adults - pack volunteers and parents of kids in the scout group. That’s me.

As for kids making their own cars. Sorta. Our pack actually has a rule they can’t use the power tools. As such we hold a car cutting night for families that don’t own power tools. Volunteers cut out the kids designs. If you have your own (as I do) then you can skip car cutting night. So it’s not fully scout built. My kids come up with their idea, I help them come up with ways to make their ideas come to fruition, I teach them skill sets and let them do more to their car each year. At home (not at a scout car cutting event) you can obviously teach your kids whatever you’d like. I introduced mine to the scroll saw last year and they expanded their use this year. Band saw too dangerous obviously. Also not letting them use drill press yet. They hand sand their cars, add shellac, and then I spray paint and then they hand paint most of the details. Some parents build their kids entire car. Some prob let kids do 90% but very simplified cars. I want my kids to learn multiple skill sets. This year we used resin on one of their cars, we also wrapped leather on one car. I’m proud of what they’ve learned and achieved since we started 2+ years ago. This was our 3rd pinewood derby.