Playing with babies is good. You won't really be disappointed because you don't expect much from them. Even if they reject you or something, you can always comfort yourself with the fact that they don't know what they are doing. They are young and innocent. And maybe they just don't know how to express themselves properly.
Actually, the only 'person' that doesn't disappoint is God. Through the ups and downs in my life, I've realised that God is always there. He never forsakes me the way I forget about Him whenever I become busy or something crops up.