Scratching my head, but I will bite.
Firstly, you say your kids are B students. Are they even in high school yet? It’s way too late for a 529 frankly.
If your kids are still in middle school, they can become A students. Then they will be able to attend college for peanuts at a college that offers full rides or full tuition to A students. That’s nifty.
Or your kids can take and pass AP exams, enter a public u with some credits already, and save you some money. Maybe they can also take CLEP exams and test out of Gen Ed’s. Then maybe they could finish college in 2.5 years instead of 4. Look up CLEP at College Board’s website.
Or they can work a lot during summers, apply for scholarships, go to CC and transfer, which will save a lot of money.
They can do military service and attend college courtesy of the government.
They can attend college in several European countries for free or very cheap.
Your kids will go to college but you have to think outside the box.