Bathroom stops with young kids?

I am going to be driving with 2 small children ages 3 abd 5 and an wondering when and where to make bathroom stops. I don't want to have to stop a million times. I mean what do you think is more appropriate. Kids going in their pants or on the side of the road for everyone to see. I mean wet pants can be changed and plus their kids so everyone will think that they just had an accident.