Here are some online resources that you might want to check out:

artforkidshub.com

Google Arts and Culture

colorwithleo.com

kidsthinkdesign.org

metmuseum.org

moma.org

getty.edu

artprojectsforkids.org

 

These are some fun digital art-making websites:

bomomo.com

scrapcoloring.com

aminahsworld.org