Use math while playing games with your children. For example, get a few rolls of pennies and have them do some math problems using the pennies. If they get the answer right, let them keep the pennies. As an additional reward, take them shopping to spend their pennies at the end of summer. To help keep them in reading and writing mode, have them help you write a story over the summer. Take turns making up the story and have your child write it out. Create an actual book with cover and all at the end of summer to show off the story and have your child read it to you.