The Bible gives us ample reason to rejoice that our God is happy. For example, when Nehemiah encouraged the people of Israel, he reminded them that “the joy of the Lord” was their strength (Nehemiah 8:10).
When Jesus told the Parable of the Talents, the faithful servant heard this judgment from the master: Well done, good and faithful servant. You have been faithful over a little; I will set you over much. Enter into the joy of your master (Matthew 25:23, my emphasis). The master's joy!