If my wife and I file a joint return and I have charity contributions, will they still give us a tax credit for those contributions or would it be better to file separate returns?

You can deduct charitable contributions on Schedule A up to an amount equal to 50% of your adjusted gross income. In general your tax bill is lower if you file as Married Filing Jointly as opposed to two separate returns of Married Filing Separately, but you can always run the numbers both ways to see which works out best for you. Note that your charitable deductions qualify as a tax deduction, not a tax credit.