I am Da-Da
My daughter has a book about lullabies. In it, the protagonist (a little girl) gets ready for bed by picking up her toys, taking a bath, putting on pajamas, and reading a story. On one page near the end, her father picks her up to place her in her crib. It's on that page that my daughter says "Da-Da," recognizing that sometimes, it is her own Da-Da that puts her in her crib. And that is why if you plan things in the evenings, between 5 and 7, I won't be there. It's why chocolate ends up on my white shirt (after taking an unplanned trip to Pinkberry - one-year-olds love that stuff).
It's also why I travel to speak at conferences and write books and wake up at 5 AM each morning so I can sneak in just the right amount of work before someone upstairs wakes up at 7 and is ready to have some milk and cereal.
There is a difference between happiness and meaning. You can have each without having a kid; but I don't think you can be happy without some kind of meaning in your life. Of course, meaning - however you define it - doesn't always bring fun. But I promise that your life will be much fuller and more rewarding if you have a point. For me, it's that my daughter recognizes why I do what I do.