Yes you can withhold any way you want since the allowances claimed on the W-4 do not need to be the same as the exemptions & filing status on the return.
In fact many married people need to with hold at the higher single rate if both parties work and have few deductions since the married withholding charts are written for a one income family. Read the W-4 carefully and review the 2 income section so you both withhold the correct way.
