We sometimes play a custom "Wingman Mode" with our 5 year old. I can't recommend this invention highly enough. My wife and I will hang back and do everything we can to run interference so our son can win. This includes ramming others off the road, diving in front of shells, or driving backwards with a Fire Flower and picking off competitors. You get better items because you're not in first, the kid still has to participate and try, and it's a novel way to play an old game.
I do something similar for my 5 yo, it actually makes for a more fun challenge than just stomping the 50cc AI. until he starts the smack talk, then he gets rekt
I believe they were added in MarioKart 7 (for the 3DS) and are also available in MarioKart 8 (for the Wii U and Switch)
