Up until this past Christmas, I flew Southwest just about twice a month for work. They have the BEST rewards program that gives you a free flight voucher for every 8 r/t flights you take in a 12 mo. period (4 r/t if you book and pay online). I am using 2 vouchers next week to go on vacation to Seattle. Anyway, I have never been put off by the open seating and in all the places I've flown, I've found everyone to be polite and cordial (no shoving). When I fly, I often see parents boarding with children anxiously looking for seats together. Since so many of the passengers are business travelers, we often would change our seating to accomodate the families (hey, we have kids too and know what it's like carting them around). I once arrived in Birmingham, AL and my luggage didn't make it (2 days before Thanksgiving...what was I thinking when I checked in 1 overnight bag I could have easily carried with me??). I was actually visiting one of my stores in Montgomery and driving there directly, so Southwest took my numbers of hotel and the store and called me that evening that my luggage made it and they would drive the 2 hours to deliver it to my hotel that evening!! The bag arrived about 15 min after I checked into my room.
About the plane ride itself, I have experienced a couple of bumpy rides, but no more bumpy than other aircrafts that experience turbulence. Since I would often take the first flight out of the day, I often slept during both takeoff and landing.
Overall, get there early and you won't have a problem getting good seats. Don't let the "suits" intimidate you...they often are hanging around the boarding area. I didn't have a problem hanging out by the first group boarding section right when I checked in. Sit on the floor for 30 or 40 min and play with your kids. And enjoy the savings where you'll really know the difference...
One more thing...pack a lunch if your flight will be during a meal time. What airlines serve surely won't be as tasty as what you could prepare yourself. My kids LOVE lunchables and think that's the biggest treat there is.