Learning from your kids through the experience of raising them, and learning from the experience of sharing of life with other human beings in general, is one thing.
Your kids sitting you down at the table and teaching you things that you should have taught them is totally different. We're talking finances and decision making skills here, not new tech gadgets and photography apps.
You can soap box your ideal life experience with your wonderful, insightful and wise kids all you want. But encouraging someone to expend their energies on a lost cause, relatives as they may be, is bad advice.
The whole point of this site is about debunking typical belief systems and behaviors that result in poor financial/life decisions. Since OP is engaging in the same activities over and over again ("teaching" her parents about finance), expecting different results, maybe its time for a change of perspective rather than more of the same (manipulating finance figures).
It has been said that doing the same thing over and over again, expecting different results, is the definition of insanity.
I don't see the difference, really, and you are totally off base to think it's egotistical. Clearly OP is better at money than her parents, and later, she's explained why (her life experience). I'm better at engineering than my parents, my mom was a much better gardener, my dad better at fixing cars. Etc. etc.
I think it's difficult when it's such a close family member - for more than one reason.
#1, it hurts to see someone you love suffer like this, when you know there's a better way. And it's probably not that her parents are stupid, just uneducated in this particular area.
#2, their lives are intertwined, albeit less so than at first with the child care. (And as far as summer care goes, it's possible that it was cheaper than other options). They owe her money. They are going to continue to ask her for money. It's going to be very difficult to "cut them off" financially but not emotionally.
I have a great, talented friend who is a dietitian. She once told me that many years into her career, she learned about phases of learning and change. She realized that there are several "phases" and some people JUST AREN'T READY. She learned to identify which people would come to her and want the magic bullet - they were not ready to make changes - and which people were ready. She actually took seminars to be able to identify these traits.
This seems similar. OP's parents have to be ready.
My 10 year old teaches me stuff all the time - computer programming, chess, baseball, all about the largest volcano ever in the world...