All trips take planning and a road trip is no different. Think about what your kids like to do, their ages, how long they could probably be in the car without breaks (also think about bathroom stops!), how long you want to drive for, and how much time you have off. The time factor is huge as you do want to have some down time and not be driving for a week straight, after all it is your vacation too!
My favorite thing is to pull out a map or pull up Google maps and zoom out far enough that I can still see where I am located but also what is in the area. Are there any town names you see that you've never visited? Quickly pop them into Google and see if there is anything recreationally that may interest yourself or the kids. Also look at bathroom and restaurants along the route to make sure nothing is shut due to COVID regulations that may cause you issues. Kids have short attention spans and bladders so make sure that you would be stuck driving for hours to find a rest stop because the one you knew of turns out to be closed.
Another fun way to break up the trip and save money is to look for parks or rest stops with picnic areas. It is super easy to make some sandwiches, pack some snacks, a few drinks, and the have a meal break / leg stretch in nature. Think about looking out for beaches, zoos, waterparks, roadside stands, unique area attractions (ex. goats that live on someone roof, the worlds largest ball of yarn, etc) and other things that might be interesting along the route that also gives you an excuse to stretch your legs.
Also, do not forget to pack snacks! A little ones stomach doesn't hold as much as yours and their metabolism is faster so they are guaranteed to become hungry more frequently and you might not have an option to stop. Things like popcorn, veggie straws, and cereal make great snacks plus you do not have to worry about keeping them in a cooler. Who cares if they are left in a hot car all day?