By "maxing out your 401(k)", do you mean you're contributing enough to get the maximum match, or contributing up to the $18,000 limit? If the latter, you won't be able to make more Roth contributions to the 401(k) on top of your traditional contributions.
At your income level, even with a pension, I'd encourage you to contribute as much pre-tax as you can. If you end up having more taxable income during retirement than you do today (>$200k), that's a pretty good problem to have, but that seems unlikely unless you work and save way more than you need to.
Once you've both contributed up to the full $18k limit toward your 401(k)s, then you can consider Roth contributions to your IRAs, likely through the backdoor since your income is so high.
In general I think 529 contributions should be at a lower priority than retirement account contributions unless you get a state tax deduction for the 529. The tax code gives you some favorable options for withdrawing from the retirement accounts early, especially for educational purposes, and the FAFSA completely ignores your retirement accounts but not your 529. But at your income level it should be possible for you each to contribute $18k to a 401(k), $5.5k to an IRA, and still have some money left over for college savings. Time to flex those frugality muscles and get it done!
I'd put post-tax investing after all those other options. Tax shelters are nice. Use them.