Socially Unacceptable

Lately Joey has displayed some less-than pleasant behaviors in public places and I'm wondering what can be done to make him more aware of what we can and can't say/do in the company of others. 

For example, while we were out to dinner last week, Joey said, "there's something wrong." We asked him what was wrong and while tugging at the backside of his pants, he announced loud and clear, "There's something wrong with my butt."  We all laughed of course, because it was so unexpected and candid of him, but inappropriate nevertheless.  Another example: Yesterday while I took my crazy train (3 kids in 1 cart) to Walmart, every 4 minutes or so Joey would shout out from the back of the cart, "I have a booger!" He yells this at me whenever he has the slightest bit of moisture in his nostril, and follows it up with, "Get it, get it Mom. Get my booger!"  I explained to him that he doesn't need to be shouting about boogers and he can just ask me for a tissue, but he obviously enjoys saying booger (don't we all?) and now just says it more often when we're home or not.

A couple other bad habits that my kid displays in public includes but is not limited to: butt scratching, telling me he's going to spank me if I say that to him one more time (where the heck would he learn that?!?!), "tooting" followed by an announcement that he did, and removing his socks and shoes while demanding that we "pell his stinky feet."

I know that this is normal, and there are probably many other mothers out there who go through mortifying moments while shopping or dining with a loud, energetic 3-year old boy.  What are we supposed to do though?  Keep them cooped up in the house until they grow out of it?  Wait a sec.  They're boys.  They will never grow out of it.  I have a feeling the inappropriate language will just get more foul, and the gestures and bad habits will just get worse.  I mean, what man doesn't think that farts are funny, and scratching or "adjusting" as we call it in my house, is completely fine to be done in the presence of others?  So I guess at 3, the apple doesn't fall far from the socially unacceptable tree.