It's not unusual for parents to make gifts to their children. Sometimes these gifts are made to custodial accounts under the California Uniform Transfers to Minors Act. Many times these gifts are made by one spouse or the other without much thought to the premise that the gifting spouse assumes the other spouse would consent (or the dollar amount isn't really worth fighting over).
While it is true that gifts made by both spouses mutually don't require consent, some might consider taking an extra precautionary step of documenting that consent when making a gift to to a minor child (or other third party for that matter) in order to prevent one spouse from claiming lack of consent to the gift.
How do you ensure you got consent?
Simple, just obtain a document which contains the other spouse's written agreement to make the gift to the third party. Having this in writing can not only make sure that you and your spouse are on the same page, but it will also ensure that the gift remains valid and not subject to later attack.
With statistics showing that disagreements about money is a leading cause of divorce, it may even even help to foster a healthier marital relationship.