Are you sure these are carpenter bees? The reason I ask is because a) there are many species of them, and b) they are super beneficial in the gardening world because they pollinate flowers.
The males buzz around wood areas, because they prefer to burrow in wood, trees, and lastly the ground. The males appear aggressive; however, they cannot sting so it's really just a show. The females are too busy hangin' with their sistahs and having the guys do their work, so they only sting if handled. They don't defend the nest, that's they guys job. Isn't that crazy?
Here's a handy link from U of Missou about them and identification:http://extension.missouri.edu/publicati ... px?P=g7424
If they sting and gang up on someone, then we're looking at a different stinging insect that will require the use of a professional. Ground hornets are super territorial, and will happily do a group sting. They like to make nests in the ground. We had a nest in our side yard last year and they all got Mr. J. a number of times. If they are forced to move and live through it, they'll just move to another section of your yard, so this isn't something to play around with.
UFL link about ground hornet identification: (I dislike them already--they kill cicadas)http://edis.ifas.ufl.edu/in573