Bring em. There were lots of kids tagging along. we were not the only ones doing the trails with babies on board. The kids loved the bumpy ride, rocking and rolling side to side. In fact many times they fell asleep.
But the secret is.....DVD. We took 20 or more videos with us and the kids had snacks and watched movies. The youngest was 10 months or so, so he was rear facing in the middle looking at the other two for entertainment. The Dog also came for the ride too
The trick when your driving is to start bloody early. We typically lifted the kids out of bed and stuck them in the truck with a dvd playing. Then we stopped for food and bum cleaning in 3 hrs time, after going a good distance already. We also made sure to stop at lots of parks for a play. That would refresh them enough to endure more movies and snacks.
We also found we needed to end the day of driving at 3pm. That gave them time for more of a play while set up camp. Then we would cook dinner and eat. Then pajama time, with another dvd....LOL and they would go to bed. Then I would sit outside enjoying a glass or three of vino.
We also found it works better on the kids to alternate traveling days. So pick a good destination then check it out for day.