They did show a gap in the security scheme; whether the gap was primarily in the hands of the Secret Service, the White House staff, or someone else is yet to be determined. Several members of the Uniformed Service of the Secret Service are on involuntary leave at the moment, while this is being sorted out. The Director of the Secret Service has accepted the responsibility (as is right) -- but I suspect, in the end, there will be several people both in the West Wing and in the SS who pay the price.
They had no invitation, and it is currently rather clear that they had no reason to think there might have been one. What they had was plenty of chutzpah. There's strong evidence that it's not the first time they've worked their way into functions; among other things, Micheala Salasi has been claiming to be have been a Washington Redskins football cheerleader, going so far as attending alumni functions and performing as an alumna... but there's no record of her ever actually being one -- and nobody who remembers her having been on the cheerleader squad with them.
Meanwhile, there are significant questions being raised about his charity polo match, and I can't help but draw some inferences from the on-going court drama regarding the winery.
All in all... to me, these two exemplify the problems with the relatively recent notoriety/infamy of reality show stardom. People have become celebrities not for what they've done, or what they do... but simply for being celebrities. Of course, they start doing more and more outrageous things to stay celebrities...
Oh... and as for criminal charges... What are you going to charge them with? Some form of trespass? They were admitted. Crossing a police line? Same problem. I'm sure there's probably some federal charge about entering the White House grounds without permission or authority -- but they didn't jump a fence; they were let into the grounds through a gate.
