They were hand picked by the Secret Service after an extensive background check. The bitch wanted a photo op with male soldiers but the secret service recommended against it. Eating utensils can be weapons "you know."
Somehow I doubt this. I've been through a couple of these with WJC, his wife, SecDef Perry, Joulwan, and other notables. The soldiers are usually chosen by their commanders and there's one of those "don't *** up" briefings ahead of the lunch. Never saw SS do a background check on anyone before lunch though.