I don't think they'll be eligible for much financial aid.
Have you checked out:
https://fafsa.ed.gov/FAFSA/app/f4cForm?execution=e1s1 ? If you could get to FIRE *before* the tax year used for the first kid's FAFSA, is it possible you could get your taxable income low enough for aid?
We have two in college now and neither is eligible for meaningful financial aid either. We were able to stuff away a pretty sizeable chunk in 529s for each kid, and then each kid also has a UTMA account made up of assets that were gifted from grandparents / great grandparents when they were little.
If I had it to do over again I'm really not sure whether I'd do the 529s. The appreciation in those accounts wasn't that much, and now there's a bit of a "use it or lose it" feel to the money that encourages spending (the threat of the penalty). On the other hand it's nice to know that that money is "theirs" for education. While we could've plowed the same money into after-tax savings, I think from a mental perspective I'd be a lot stingier about spending it for college because it'd feel like "my" money instead of "theirs." I think if we had gone that route (brokerage savings vs 529), knowing what I know now, I'd definitely suggest keeping the college money in a different account, even if it has your name on it (i.e. your retirement $$$ with vanguard, your college savings with fidelity) just from an emotional accounting perspective.
Unfortunately you don't have to make THAT much to be in the same financial aid situation as Bill Gates. I cannot fathom spending sticker price for a four year private education at a name brand school. Shoot for your 6-8 year olds it wouldn't surprise me at all if the top schools were 80k a year "all in" by the time they are heading off to college. Unless you KNOW your kid is going to be the next Speilberg or Zuckerberg or Gates or Clinton, I can't see spending that kinda cash on an elite college.
My oldest has certainly been challeged at a state U in a nearby state where she got some decent scholarships and kept the price roughly inline with going to the local U. My son will be attending a four year private school (not quite "elite," but selective) next year on an academic scholarship. Haha be better be able to maintain the required gpa because it would be very difficult to pay the retail price.