Check out Shannon's site,  Rocks In My Dryer, for lots of great tips!

Travel with youngsters can be a challenge, especially when Dad's moving at a great pace, mind set on reaching his destination, and someone suddenly has to go.  Moreso if we've just barely left the last pit stop.  Or, running errands with a van full of children, no restroom handy, and someone starts wiggling!  The boys aren't too tough.  In an emergency, they can usually relieve themselves with minimal stop time and just a little privacy.  The girls, not so easy.

When stopping  just isn't an option, an empty water bottle is helpful...there's something about boys and bodily functions.  They find great humor in being able to take care of business, and I just don't relate.  The other day, though, we discovered a reasonable not-too-humiliating solution for the girls.  We keep a small plastic garbage can in the front of the van, between driver's and passenger's seat.  A plastic grocery bag inside of the can holds the trash.  Remove bag of trash, and behold, instant porta potty.  A relieved (pun intended) 8 yo dd was a little reluctant, but desperate enough to try it.  Business finished, contents emptied in the desert parking lot, and can wiped out with paper towels (another essential in our vehicle), the problem was solved without damage to the vehicle's upholstery!  Just need to add a can of disinfectant spray to that list of vehicle essentials!

A new solution to a very frustrating problem, this definitely works for me!