Traveling with baby and toddler!

We are taking a trip next month with our (almost) two year old and 3 month old daughters. It'll be a 16 hour car trip (6 hours one day 10 hours the next), our three month old is still nursing but if I pump she'll take a bottle. The oldest one has been on long trips before, but not since she was 6 months old and I'm a little nervous with how to keep them from getting too restless with such a long drive. We only allow them to watch movies as a last resort and don't let them have any other kind of screen time. I'd appreciate any tips or tricks people have for taking long trips with little kids! Thanks!