No, because people in their 30s are more likely to have issues with the lifestyle
First, my bona fides: I'm in my mid 30s, and have been a lawyer for around a decade, split roughly 50-50 between litigating at a V20 firm and doing appellate work for the government, with an AIII clerkship thrown in as well. I'm also married to a non-lawyer prestige professional (think doctor or professor) and have three kids -- we wanted to stop at two, but sometimes there's two blobs on the ultrasound.
Second, the bias against older entry-levels is not a myth. My dad is a senior partner at a 30ish attorney satellite office of a mid-tier firm, and has done a couple of stints as hiring partner. He flat-out told me that they wouldn't hire a first-year over thirty unless they were sure that family wasn't going to be an issue (e.g., someone who is divorced or gay without children). Similarly, he also said that while they are happy to hire younger married women, it's generally assumed that those associates will only be able to work 4-6 years until the second kid comes, with a six month break for the first kid. Of course, my dad is a late 50s/early 60s male who was raised in the south, so his views may not be representative of law firm management as a whole.
Third, and most importantly for this thread, I think that the idea that one cannot balance a biglaw career and a family is wrongheaded, with two caveats. Yes, you work a ton of hours. But you also make a ton of money that you can use to pay someone to watch your children, and once they're in school, you're probably only missing a couple of hours a day compared to a 9-5. If that -- one thing that people forget is that most biglaw attorneys have the mornings with their kids, which is something that someone who has to be at his desk by 8:00 AM doesn't. So yes, you're missing the 6:00-8:00 PM hours that other parents get, but you're also there from 6:30 to 8:30 in the morning when most non-lawyers are commuting.
Caveat 1: If your spouse is a stay-at-home parent, you're probably going to get divorced if you have young children. I almost got divorced when I was billing 2400 a year, and that was pre-kids. My spouse wouldn't last nine months now that we have the gremlins. At some point, when they are taking care of the children and cleaning the house during all waking hours, and their sole "adult" time is basically sitting in front of the TV with you from 9:00-11:00 PM as you scarf down some greasy leftovers or takeaway and try to vege out (read: ignore them) after a twelve hour day, they're going to realize that divorce means one night a week and every other weekend free, and a boyfriend/girlfriend whom they actually get to talk to. Either that, or they go batsh!t crazy, and you're the one who initiates the divorce proceedings. The fact of the matter is that biglaw associate spouses tend to be relatively young and well-educated and have had a career of their own prior to kids -- in other words, probably the least-suited people imaginable to be stuck at home with kids and nothing else from 8:30 AM until bedtime.
Caveat 2: If you both work and have young children, you have a much better chance, but accept it up front that your kids will be raised by nannies/pre-schools. That's not so bad for the kids if you have a quality nanny/pre-school (for our first, we found a great Waldorf school, and for our twins, we hired a wonderful woman whom they now call "second mother"), but the idea that your kids are getting raised by someone else takes some getting used to. Especially for the moms.