Well then.......you might like to try this - something that worked very well with my children when vacationing.
Age determined how many quarter rolls they were given. Mostly just one or two rolls. The money was spending money for souveniers/treats....AFTER arriving.
During the trip...........I had a "penalty box".
Anytime they started to argue..........complain........or say a bad word - the Penalty Box came out.
The very first time I used this method.....only ONE quarter went in it.
The majority of our trips were quite pleasant.
Of course, once in awhile, I had to ask:
"Need I get the Penalty Box out?"
The age of each child and how bad the violation determined whether or not they received a verbal warning or had to pay immediately. (After all - long trips can get on everyones nerves.)
My daughter liked it so much...........when her and a friend had to take a niece on a long trip.......they used it. She thanked me. :o
Anyway, that was why I asked the nosey questions...thought maybe my idea might come in handy for you.