Recommended venue is Arena, followed by Crystal Pools, Redrock Cove, and Scorched Forest. Golem Workshop isn’t a bad choice either if you want a challenge. Data from here. Thread about holiday chests, their contents, and their locations/mob drops is over here once the holiday starts.
(19%) Training Fields - Glowing Pocket Mouse, Sweetpuff, Amaranth Moth, Bumble, Ceanothus Brawler
(23%) Woodland Path - Grouse Basilisk, Strangler, Wildwood Owl
(27%) Scorched Forest - Crowned Bonepriest, Augite Protector, Extinguished Jackalope, Red-Winged Owlcat
(25%) Sandswept Delta - Crowned Bonepriest, Greatshell, Serthis Potionmaster, Peacock Scorpion
(24%) Forgotten Cave - Citrine Jewel, Crimson Reef Snail, Deepmine Aardvark, Venomblade Assassin
(16%) Bamboo Falls - Trick of the Light, Tengu, Tigerblood Foo
(30%) Redrock Cove - Leopard Coralclimber, Maren Spearmaiden, Mirage Puffer, Noxious Coralclimber, Waveswell Sorcerer
(19%) Waterway - Noggle, Maren Currentfinder, Radioactive Slime
(40%) Arena - Celestial Antelope, Featherback Boar, Goldenplains Poodle Mith, Longneck Mender, Charcoal Sprangyroo, Chimera, Double-Tailed Warcat
(24%) Volcanic Vents - Flamescale Lancer, Serthis Archivist, Armored Duskflapper, Basalt Vent Hop, Flamescale Illusionist, Ghost Manticore
(18%) Rainsong Jungle - Goldenbeast, Hippocampus, Parda
(21%) Boreal Wood - Snowfall Elk, Longneck Hunter, Winter Wolf
(30%) Crystal Pools - Crystalplate Stinger, Almandine Sturgeon, Clearwater Oracle, Moonbeam Crayfish
(25%) Harpy’s Roost - Stonewatch Harpy, Cardinal Hippogriff, Dodo, Mesacliff Harpy
(26%) Ghostlight Ruins - Lux Spectre, Carrioncorn, Disoriented Spirit, Greybeak Reaper, Longneck Medium
(25%) The Mire - Brilliant Psywurm, Shellion, Southmarsh Podid, Wetland Unicorn
(20%) Kelp Beds - Golden Porpoise, Depin, Mammertee
(28%) Golem Workshop - Swift Lumen, Monkey Wrench, Sentry Squawker, Steelhound