Can we please not call them "Caskett?" Those shippy portmanteaus are annoying enough as a rule, but that one's downright morbid.
I didn't care for this one. The idea of mixing up the characters into different groupings was a nice one, but the execution was too silly and corny. The detectives dressing up as Elvis impersonators to get into the casino? Really? Couldn't they have just liaised with the Atlantic City police and let the local detectives go in and ask the questions? And Fillion looked really bad in his Elvis disguise. Is he putting on weight? He seemed huge.
And the "teen party gets out of control" trope is extremely cliched and predictable, and I thought Alexis was out of character at the end. She wouldn't lie to her father about it, she'd admit her mistake and take full responsibility. I miss the Alexis of the first three seasons, the one who was the most levelheaded and responsible member of the family. She seems to have been replaced by a far more stereotypical moody, erratic teenager.
Also, having the captain directly work with Beckett in the investigation on their end was contrived. Surely there are other detectives in the precinct that Beckett could've teamed with. And if there were so many crimes under investigation that none of them could be spared, then surely the captain would be too busy overseeing all of them to devote herself to just one. At least they made a token effort to justify it by having her say she liked to visit the trenches now and then. But it still felt awkward.