401k for kid's college tuition

I have a 2 year-old son. I have had several people suggest that I open up a 529 account to pay for college. My wife and I both pay into defined benefit pension plans (lucky me) and we also both have a 401k to supplement the pension. It seems to me that it would be easier to just use my 401k to pay for his college instead of opening up another account since I will most likely be retiring just as he starts college and I won't be relying on the 401k for my retirement income. But I know a lot can change between now and then. What are your thoughts money board?