Lovely idea for traveling with kids: a travel journal with lots of activities, prompts and ideas that also included envelopes for collecting tickets and other treasures. Check these free printable pages.
Toddler Road Trip Activities: How $2.25 Bought Us 4 Hours of Happy Silence
Stop screaming at your kids! Road trip clips: One clip for each kid. If they are sweet, clip stays up, if they are not, clip comes down. Everyone with a clip on the visor gets a treat at the next stop (or whatever reward idea you like)
making these trays, for a cookie tray and some contact paper from the dollar store. just need to figure out a velcro system to keep them close at hand and keep them from falling off their laps while driving.