Don´t bring the whole beach home with you.

To minimize the amount of sand that you get in your car or track through your house after a day of beach fun, first use the end of a towel to brush sand off of children´s feet - and your own. If there are shower or rinse facilities at the beach, wash excess sand off there. If not, consider using a hose before going indoors at home. Alternatively, you could keep a bottle of water in the boot/trunk of your car specifically for rinsing off sandy feet. If none of these options are available (or appeal), and the sand still bothers you, it´s worth walking around for a few minutes to help the sand dry and become easier to brush off.