Your income taxes will be very low, hardly worth worrying about.
As others pointed out, your list of deductions is a bit off. You will receive the following deductions:
* Standard deduction: $12,200 in 2013 (and indexed for inflation in future years)
* Personal exemptions: $3,900 each for yourself, spouse, and dependent children (college students still count as dependents as long as you pay at least half of their expenses). If you have two kids (one in college and one still living at home), that's a $15,600 deduction in 2013 (and indexed for inflation in future years)
The sum of these two means that your first $27,800 of income will be completely free of tax. Past this, your next $17,850 is taxed at 10%. So if you have $45,650 of regular income, you will owe only $1,785 in income tax, or a 4% effective tax rate.
This number only applies if all of your income is "regular income" (i.e. wages, interest, distributions from traditional IRAs/401(k)s, short-term capital gains, etc.). For people in your tax bracket, long-term capital gains and dividends are taxed at 0%. If you have $27,800 or less of "regular income" and the rest of your income comes from long-term capital gains and qualified dividends, you will pay no tax.
But wait, it gets better!
If either of your children are under 17 when you retire, you can claim a child tax credit of $1,000 per child. This is a credit, not a deduction. This means that it subtracts money straight from your tax rather than from your income before calculating the tax. If you have no income from work, the credit is not refundable (i.e. it's limited to the amount of tax you owe before the credit). Even so, having one under-17 child cuts $1,000 off your tax bill.
But wait, it gets better!
There are tax credits for college students, as well. There are two different options here: American Opportunity Credit and Lifetime Learning Credit. The American Opportunity Credit is usually better if your kid qualifies for it. For your income level, this credit will generally be worth $2,500, of which $1,000 is refundable.
For a family of four, with one child under 17 and the other in college, you get $27,800 of income completely tax free, you get non-refundable tax credits for the first $2,500 in tax, and you get a $1,000 refundable tax credit on top of that. This means that if your gross regular income is $50,416, you can subtract $27,800 to get your taxable income of $22,616, which translates into a tax of $2,500, which is negated by your $2,500 in non-refundable tax credits. Then you get a $1,000 refundable tax credit, making your total tax for the year be $-1,000. That's right, you can have income over $50k and pay taxes of negative one thousand dollars.
Remember also that long-term capital gains and qualified dividends are taxed at 0% up to $72,500 in taxable income. This means you could have an additional $49,884 of this type of income on top of your $50,416 of regular income, and still have a total tax bill of $-1,000.
One practical consequence of this for an early retiree is that you should take advantage of your tax-free thresholds as much as possible. Once your kids finish college and no longer qualify as dependents, your threshold for tax-free regular income will get a lot lower (it's only $20k for an under-65 couple with no dependents or tax credits). When you get $50,416 of tax-free regular income, use that limit to its fullest. Roll over part of your 401(k) into a Roth until you get up to that threshold. Sell some stocks that you've had for more than a year until you get to the $49,884 threshold as well. Re-invest the proceeds in the same funds if you wish. There's no sense waiting for next year to realize income when you can do it tax-free today.