Make sweets and dishes for Krishna ji.
Decorate the idols with new clothes and jewellery. Don't forget to decorate the jhulla too
Dress up the kid as Krishna or Radha
Draw a Rangoli & make tiny Krishna footsteps leading to your house .
Let your kid paint the pots for dahi handi
Read some fun books on Krishna
Do an interesting story telling with your kids and include some craft work too.
If your kids are fond of playing with playdough, let them make a little Krishna with it.
Help your kids make their grandparents a cute little Janmashtami Card,