I am 34 and in a similar situation. I would max out the 401K and Roth IRA's before paying off the mortgage.
I am at the point where my 401K and Roth IRA's are being fully funded. I am using any additional funds toward a 529 plan and paying off my mortgage.
I chose the Iowa College Savings 529 plan. It is run by Vanguard and the fees are less than other plans. You do not have to live in Iowa (I don't) and the funds can be used for schools across the country. You can start with as little as $25. Also, you can link Upromise contributions to this account. They have some great asset allocations (index funds). You may want to check out www.savingforcollege.com
. It was very helpful. Good luck.