Bubble wrap (the kind with large bubbles)
A4 sheet of paper
Scissors
Double-sided tape
Pencils, markers, crayons

Cut a piece of bubble wrap so it fits over the sheet of paper

Using the bubble wrap as a guide, draw images on the paper of different road trip sights/items from nature, etc. Get the Cubs involved by talking about what you might see on a hike/road trip and asking them for suggestions (even if you're unlikely to see one, keeping them on the lookout for an elephant could occupy a lot of time). Depending on their age, use colors, numbers, letters and symbols to give the game an educational element. If they are old enough, kids can draw the images themselves — or give them a sheet to make their own game. If you're not comfortable drawing, find clipart online to print or cut out pictures from magazines and glue them in place.

You can premake one and make color copies of it so you'll have multiples for all the Cubs (instead of making it with them)

Put double sided tape around the edge of the bubble wrap and stick in in place over the images.

When you're traveling/hiking, kids can pop the bubbles as they spot each of the items on the sheet. If the Cub doesn't have the patience to wait, they'll still have fun looking at the pictures and popping the bubbles on their own time.