Stay POSITIVE! -- Having a Family is MORE fun!
Take the positive approach. I have eight children. Been there, done that, and doing it again.
Far more fun to play games with your kids - especially when they are young and the world is "new" - I would never exchange that for some silly "party" on Friday night with a bunch of jaded adults that confuse pleasure with happiness in a billion years!
When people make these comments, they ASSUME that whatever they are doing is more fun than what you could possibly be doing because they really don't know what they are missing.
Who can blame them?! You should not be negative to them. They just don't know.
So, just tell them: "I have far more fun with my family than I ever could at a some party, so I choose the family." (For fun, say it in a Godfather voice to impress the importance of "the family". ;) )
As far as reading for pleasure - "I do that in the evenings, when the kids are in bed, but you know what is more fun? Finding that mouse in Goodnight Moon with my kids!"
As far as hobbies - "I have a great time sharing my hobbies with my kids - it is so enjoyable to share them with others that appreciate them! And, so fulfilling when they do it themselves!"
As far as breastfeeding - "Hey, I want to give my kids BEST chance, and NOTHING beats a custom made drink from Mom!"
ETC
In other words, look at all the blessings, fun and happiness and share that (in aa POLITE way) with the folks that look down uponon you.