Your child is pretty young to be so interested, so DEFINITELY bring the chair! Even if he does not use it on the trip (when he would have to signal you to quickly pull over and you could dash to the side of the road and place him on it), you will defintely have time to place it in your vacation venue and see if he transfers his knowledge and interest to use it. But please, no pressure at his very young age. A portable DVD or a 10-12" cheap 12V TV with favorite movies and a splitter with 2 headphones was a classic for our kids. We would collect films and videos before the trip, NOT watch them at home, and then they'd be 'fresh' for the road. Our trips were 14 hours by car with two male toddlers, for several years, and a pottyseat and small TV w/tapeplayer were essentials!! We also did things other people mentioned with sticker books, magic writing books where they scribble on what appears to be a blank page and something appears, plus each with a backpack full of little toys---some which they picked to pack and others which we wrapped to be opened each hour as a surprise. If part of your travel can be at night or in darkness, that is another plan if they can settle in for a few more hours of sleep. Have fun!