Happiness is being free from vexations, able to be and act without artificial limitations, manifesting the mind's pure innate freedom.
Simply giving things away may not bring happiness, but with correct attitude generosity is a good way to cultivate the mental habits that contribute to happiness. Attachment to material things is a self-imposed limitation that leads to vexations, as is the notion that other people's troubles are fundamentally different from ours and thus not our problem. Therefore, giving others things that they need in a spirit of genuine care is a way to break down those barriers.
Happiness is a result of compassion. If people refuse to cultivate compassion until they themselves are happy, they will never do it. The point of compassion is to come to understand on a deep level that other people's troubles are no different from your own, that their happiness is also your happiness. True happiness is impossible as long as people build up these walls between themselves and others, thinking that life is a zero-sum game with winners and losers. It is never too early to cultivate compassion and loving-kindness for others.