Hashmal, toss them all off-balance with a series of Earthquakes! Focus most of the power on the Luxray! Atlas and Toxicroak, assist Hashmal with your own Earthquakes as well!
Airship, Ca and Delibird, focus fire on the Serperior! Ca and Airship should use repeated Acrobatics and Air Slashes while Delibird can fire off some Ice Beams to put her on ice.
Sliggoo, Dewott and Flaafy can take care of the Infernape. Sliggoo, continuously use Muddy Water and Dewott can take him head on with repeated Hydro Pumps. Flaafy, slow him down a bit with a Thunder Wave and then some Thunderbolts.