Personally I would not change anything on the current old W-4 forms you have if you get the desired refund now ... adding a dependent will only make it sweeter. You are not required to change anything on the W-4 at all. If you are going to change then you both need to change with the new W-4 system so use this tool to figure it out ...
Use the Tax Withholding Estimator on the IRS web site to figure out what you and your spouse should each put on the W-4 forms that you give to your employers. It's much easier than using the worksheets on the form. It will let you adjust your withholding to get the approximate refund amount that you want.
