IME, 2 yo's need a cruise director unless they are sleeping. Someone older needs to sit with them and actively entertain them; b/c they tend to get fractious if no one is talking to them when they are awake. They usually cannot operate the quiet toys well without help. So ...
With that range of kiddoes, I'm going to guess that they are driving a van. If so, my best advice is for them to put one car seat in each rear row, so that an adult can take turns with the 13 yo sitting in the back. (Perhaps also the 11 yo, depending on her size.)
It is also a good idea to scope out park playgrounds on their route, and hit them after the little ones wake up in the daytime, to let them burn off steam.
What we found to be the very best strategy at that age was to book a hotel with an indoor pool en route, and make sure to get there early enough to swim. Swimming is one of those things that relaxes adults but exhausts small children, and it was the only foolproof way to get them to go to sleep at a decent hour, because they had spent so many hours asleep in the car, but popped up like little bunnies the moment we stopped. Naturally, we were exhausted at that point, but the kids were well-rested, so the swim evened things out: got the kinks out of the grownups and wore out the kids.