It's ok to not know precisely right now what you are saving for, for your kids.
--Only When our oldest hit 12, we gelled on what we were saving the money for -- tuition and books for an instate 4 year degree (living at home). I wanted to be able to give her the basic opportunity for a bachelors if she chose.
--BUT, if she does something else, we can decide what to do at that time with the money.
Next, as we were thinking about FIRE within 5 years, we decided to save up for all the near term (within 7 year) large expenditures before FIRE-ing. Kids education, 5 years of annual property taxes and car/home insurance, vacation fund, and maybe even a used car fund. At your kids' age, I would add in $5k each for braces or medical expenses.
After FIRE, the savings stopped. Everything draws down the pool of retirement money, so why withdraw, then put it back into a different form of savings?