We also play it in the opposite to help him learn the "less than" side of it. In that instance I'd say, "If Brother is 10, how old is Wi-Fi"
RoadSide Reading... Since Brother is learning to read and sound out words, we've also been practicing that in the car. First it started as him reading easy books to me and Wi-Fi while I was driving, but that got "boring" so I started pointing out words while driving. Now it's become more of a game. We see how many funny words we can find on our way to where ever it is we're going by reading road signs, signs outside of stores and even on trucks. Sometimes if we're at a stop he'll even find words on bumper stickers.
Although it's not a game...
CarKits... Let's face it..sometimes mommy here needs quiet time, especially since the car also happens to be where I like to do my thinking! So I came up with a "CarKit" for the boys to ensure that when they are extra loud or hyper, I can get that. I found a couple of clipboards with storage and put some blank drawing paper, crayons/makers (for brother)/ colored pencils in there for them to draw. Most times I will give them each a subject to focus drawing or tell them to make up a story.