How to keep a child busy for hours in the summer: DIY: Giant Ice Cube Awesomeness - filled with plastic animals, dinos, and such. And I'm sure you could put in food dye before its frozen to color it like the ice block in the photo.
Play Create Explore: Baby Oil Sensory Bags = baby oil, food colouring, a little bit of water, glitter, objects to find (smooth). Put in ziplock bag and duct tape for leaks and little fingers who would like to open it. ((or a heat seal bag))
The Fun Cheap or Free Queen: How to survive a road trip with two babies by yourself.roadtrip tricks, tips, and creative ideas! (plus link within the site to more tips from a trip w/ slightly older kids)