Lots of stuff out there on the internet. Google it up and you’ll find plenty of easy, affordable ways for the kiddos to spread some kindness.
Some great places to start-
https://www.naturalbeachliving.com/random-acts-of-kindness-ideas
Cute printed cards for ideas
http://www.allstudentscanshine.com/2016/12/kindness-elf-freebie.html
Calendar of daily ideas for kids
https://www.weareteachers.com/random-acts-kindness-calendar
Advent Stockings-12 days of Christmas
https://www.muminthemadhouse.com/advent-acts-of-kindness-free-printables/
go Gently 