Reconsider, Seek. With a trailer you can haul your motorcycle around (Or, I forget, to you already mount it on your bumper?) and your kids would be quite quiet and happy as you drive along. You could even take that trip to Yellowstone you wanted to do and your kid would enjoy every hour on the road.
I actually considered this one for a fleeting moment... http://cgi.ebay.com/ebaymotors/2004...21290326QQcmdZViewItem?hash=item200221290326&
Problem --
It does not solve my issue I have with my currrent van bench seat safety. I need my children to have shoulder harnesses to fit into the necessary booster seats that they have to be in by law until 8 freakin' years old!!!
On the plus side, the potty is built in!!! I carry a camp toilet in my van now and will continue to do so.