I've been riding 20 years, not including my years as a kid on the back of my Dad's bike (not sure that's even legal anymore). Riding is in my DNA, and I plan to do it as long as I'm physically able, but I don't have kids so my perspective is different than yours. Several of my friends I rode with in my early 20s quit riding when they started a family, and a lot of the folks I ride with now are older and have grown kids, so I guess a lot of folks weigh that and choose not to ride for a while. But as someone else mentioned, aside from the safety concerns I think another factor is that most folks choose family-oriented hobbies and get a boat or something more conducive to including the kids.
But like I said, I learned to love motorcycles by riding with my Dad, so it doesn't have to be a solo activity. And a lot of folks start riding dirt bikes and ATVs at a young age, so that might be a way for you to get started riding and include everyone.
Here's what HD recommends for their denim paint: Denim Paint Cleaner | Genuine Motor Accessories | Harley-Davidson USA (check out the video). It seems Adams Waterless Wash would be the ticket, but hopefully someone else with experience can say for sure.
Apparently this is from a HD service bulletin on denim paint care: Service Procedure
Cleaning Black Denim paint:
For heavy deposits on finish:
Use a grease cutting dishwashing detergent and a clean H-D wash-mitt (P/N 94760-99). Dilute dishwashing detergent per instructions provided by manufacturer and rinse thoroughly with clean water.
For light deposits on finish:
Use ammonia based glass cleaner and a soft H-D Soft-Cloth (HD-94656-98).