I would just fully fund your Roth IRA. Contributions can be withdrawn at any time tax and penalty free for education expenses for the owner, children, and grandchildren.
https://www.irs.gov/publications/p970/ch09.htmlAdded a bit to clarify... This is my plan - right now anyway. If my kid doesn't go to college - it's still in my fund.
As far as my daughter (6yo) is concerned... We haven't decided for sure how we will work with her to fund her schooling. Here is my initial thoughts:
Encourage her to go to community college for the basics - all expenses paid. I just looked up tuition at the local community college - it's 20% of the local state school - no shit! I may even pay for a reasonable apartment for her to do this because it would still put me far ahead financially than the local state school.
Fund her books and tuition at the nearest state school (currently about 20 minutes from my home). We will provided housing at our home, food, transportation, etc.
Fund her books and tuition anywhere else she wants to go up to what the costs would have been at the nearest state school. She will need to fund any additional expenses (room & board, food, transportation, etc).
This plan helps reduce my liability, doesn't take a huge hit to my retirement plans, and forces her to make adult decisions about how to fund her schooling. It hopefully forces her to think long an hard about taking out school debt and/or working while in school.
An aside:
I've also considered going and getting my own masters degree after my first retirement, which will also be about the time of my daughter's HS graduation. This will also stretch out my early retirement funds a couple years while I start my Roth conversion ladder as well. Now that I think of it - this strategy could be a great way to stretch my emergency fund if I ever lose my job - and make me more marketable for the future.