I don't know about "pig out", but I eat until I'm fairly full. But I don't put more on my plate than is normal for me at any dinner. Though I will insist on pumpkin pie even if I'm not that hungry :P
We eat at Cracker Barrel because that's where my wife's grandpa likes to have it. And, yes, he pays for everyone. I'm not a big fan of eating out on thanksgiving because I hate being a part of having to make others work on that day. There's also no leftovers to take home because the portions are controlled. So we buy our own thanksgiving to have at home for the next day.