The big one I finally figured out is the bathroom sink. In my RV the bathroom sink dumps into the black tank.
I stopped washing my hands in that sink and stopped brushing my teeth there also. Made a big difference in how fast my black tank filled up.
This change alone added days to how long I could go without having to dump the black tank.
Have the kiddies wash hands and brush teeth in the kitchen sink which dumps into the gray. And of course 'change the habit' of leaving the water run while brushing!
At CG's - shower at the CG showers and encourage kids to use the bathroom facilities there during the day also.