EV3 mindstorms (graders, grade, course, children)

[tango14]

We are starting a FLL group for 4th graders. We have the Ev3 mindstorm kit. Does anybody have good websites/resources/books that would help us guide the children starting from simple tasks on the EV3 onto more complex projects. There is a course on udemy but wanted to see if any one has worked off a site/resource that really helped go thru all basics and slowly build up the complexity to keep it challenging and interesting for the children. Thanks.