For the Main Kids (I base this on personality/backstory rather than in the context of the AtLA/LoK world):
Sage: Earthbender
Amaryllis: Some kind of spirit
Renato: Firebender
Celeste: Firebender
Levi: Waterbender
Solomon: Firebender
Eve: Nonbender
Rhys: Airbender
Joseph: Nonbender
Tanith: Again, maybe a spirit of some sort
Emery: Earthbender
Euphie: Airbender
Tipha: Airbender
Oliver: Airbender
Maddie: Nonbender
Aster: Waterbender
Mindy: Firebender
Blake: Earthbender
Gwennie: Waterbender
Aurélie: Airbender
Thomas: Airbender
Odette: Nonbender
Xavier: Nonbender
Yvon: Nonbender
Florian: Firebender
Primrose: Waterbender
Enzian: Waterbender
Weiss: Waterbender