We just drove from MN in December! 24 hours exactly. This is our 3rd drive down as a family. My kids are 2, 4, 6, and 8.
We did NOT stop often. We tried to get as far as we could between stops, and my kids were rock stars. We usually made it 4 hours at a time without stopping. A couple of times we stopped sooner because of bathroom issues but that was rare. And our stops were quick... we weren't playing at play areas. We were out, getting gas, taking bathroom breaks, running around for a couple minutes, and then right back in the car. When you have such a long drive, you really just can't stop as much or it'll take forever.
I had TONS of food. We don't like to eat at fast food places, because it slows us down, because it costs more, and because the greasy food isn't so great when you're in the car for that long. So we brought a cooler, and we put together a bunch of rolls with ham and cheese, homemade uncrustables (
https://www.amazon.com/Wonder-Sandw...05&sr=8-2&keywords=uncrustable+sandwich+maker), breakfast crackers and pop tarts, granola bars, fruit snacks, bananas, grapes (sliced in half for the younger kids because I worried about choking in the car!), and we made cookies to bring.
I stocked up on inexpensive DVDs during the months leading up to our trip. Then I wrapped them, and let the kids take turns unwrapping the movies throughout the ride. They liked that. I also wrapped a couple small Disney stuffed animals for them to open. We did bring some activities but to be honest, the kids didn't do much except watch TV. Even the 2 year old was fine with that. Try to find TV shows rather than movies, as a 1.5 might prefer something like that. I brought Mickey Mouse Clubhouse seasons on DVD for him and my 4 year old, but had movies for the big kids. We took turns picking.
The 4 year old struggled the most with the trip I would say. He just couldn't wrap his head around how long of a drive it was, and there was a point during the trip that he was literally asking every 10 minutes if we were there yet. We were in like Wisconsin at that point, lol. It didn't make sense to him that we were going to sleep in the car. The way home was much better for him because I think he understood better at that point. But overall, I was shocked at how amazing the kids did.