As the receiver of a gift from an individual you do not report the gift received on your tax return, regardless of the amount received or the value of the gift.

The giver of a gift to an individual does not report the gift given on a tax return.

The giver of a gift to an individual can gift up to $14,000 to a single individual in a year without having to complete a Gift Tax return, Form 709.  So each of your wife's grandparents can give you $14,000 for a total of $28,000 to you and each give your wife $14,000 for a total of $28,000 to her.  So that would be up to $56,000 in a year to you and your wife from the grandparents.  They would not need to complete a Form 709 since they have not exceeded the requirement of $14,000 to a single individual.

Note - Gift taxes are only assessed after the total amount of gifts given are greater than $5,450,000 (2016)