In my experience, conferences are a very nice to have, unique experiences, interesting people. But productivity? No. When it comes to being productive, I get far more done sitting at my desk at home. I totally understand that conferences are a really nice thing to go to for contributors. But its more a sort of compensation for unpaied work. At some point, you are invited to go to a foreign country, and you get a sort of geek-holiday. Thats nice. But I never considered it essential for my contributions.
In fact, my impression actually turned around when the "bring your children" thing started to be normal. I vividly remember a few talks at DebConf where I was not able to follow the speaker because of verbal small children in the talk room. Since then, I really really prefer to listen to talk recordings at home.