Enough Federal withholdings?

My husband will have earned roughly $39,000 in 2010. I was unemployed (no unemployment comp) until this month and will earn $4,800 for 2010. Between the two of us, we'll have paid $1,788 in Federal Taxes. Will this be enough or could we owe? We changed his Federal Exemptions to 'Married 3/0' while I wasn't working since we have 2 young children. Am wondering if that is too little being paid to the IRS and if now that I'm working, we should change it? My earnings in 2011 should be approx $33,000 and his should remain the same. Thank you for your time and input.