This is the simplest ever way to occupy your kids for a few minutes.. especially if they enjoy colouring in... (one of mine does and the other isn't interested).
There are loads of printable bookmark templates on the web - have a look around and you will find tonnes of options. Simply find one you like and print off the template.
Once you've printed it off, cut out the template of the bookmark. Glue in onto a thick piece of cardboard to give it strength.
Colour it in!
Perfect for your summer reading!