There are many museums offering free tours and almost all museums have digital access to their galleries. The links below will take you to different art museums’ websites. The last link is for the Google Art Project, which is an amazing project where you can explore random art up close.

National Gallery in DC
National Gallery in London
The Louvre
Google Art Project

The following links will take you to videos about art and artists. The first is a children's TV show called Mati and Dada, designed for younger students. The second is a link to Khan Academy that host a wide range of readings and videos on a variety of subjects. I have made sure the link takes you straight to the Art and Art History section. 
Mati and Dada 
Khan Academy

This website is a drawing prompt random generator. It gives you different options and drawing ideas, try combining ideas for an added challenge!
The two links bellow will take you to two drawing tutorial channels designed just for you! They feature basic drawings and more advanced character challenges 
Doodle Academy:
Art for Kids: