529 Plan Maximum

Question: Should I invest in a college savings plan or pay back my mortgage early ?
My wife and I have 2 young children (2 and 4), we live in California and our income is around 200k/year. We owe $700k on our mortgage (rate: 6.25%, 30 year fixed) and we try to contribute the maximum to our 401ks.
what if we can save an extra $10k or $20k next year ?
should we invest them in a college savings plan (529) or should we try to reimburse our mortgage early?
I’m mostly interested in the tax benefits of these 2 approaches.
Thanks,
Al
Answer: pay off the mortagage!!!
Dave Ramsey on the 529 Plan