Thank you for your question and congratulations to you both. You will want to go to the tables for Married Filing Jointly or Separately and use the tables to determine the extra withholding on the higher paying job needed in Box 4 (c). Once you determine the yearly amount of the extra withholding using the tables, you will then divide that number by the remaining pay periods in Box 4 (c).
The Minnesota W-4MN can be found here: W-4MN
Using this form your Minnesota allowance on each form should only be 1 each.