Greetings, Patricia! Thanks for returning to the Disney Parks Moms Panel with your question!
I recently returned from the Disneyland Resort and also noticed that our
favorite friends from Cars were not on the
Disneyland app. However, I did spot Mater taking photos with Guests several times while we were there. I believe I also saw Red a time or two as well. I'm not quite sure why they aren't appearing on the app lately, but when you make your way into Cars Land, find a Cast Member with an "Ask Me About Characters" button to inquire about the schedule to meet Mater, Lightning McQueen, and Red. I also recommend continuing to scope out the app as your travel dates approach as characters can change daily.
Also while you are in Cars Land, make sure to have at least one meal at
Flo's V8 Cafe. It is one of my family's all time favorite eateries! We like to take our meal outside and around back at Flo's to have an incredible view of Radiator Springs Racers while we dine. And since your little one loves Cars, the kids meals at Flo's usually come in cute collectible racers!
I hope you and your family have an amazing time at the Disneyland Resort this fall!
-Linda M.