What kind of summer holiday do you have in mind?
A vacation?
Staycation?
Waycation?
Daycation?
Well, if you're riding in a car with kids for any length of time you might consider downloading the Simple Saturday Travel Bingo Game to use just in case things get a little hairy in the backseat. The download consists of two gameboards. Simply print off a few sheets, pre-cut before you leave, and pack a few pencils with you for the ride.
All your sweet ones need to do is look out of the window and find the objects featured on the game board. It's that easy. When they spot an object, just mark it off of the board.
I suggest that you play Black Out. It keeps those kiddies busy for a long, long, l-o-n-g time.