There are so many activities that you can do without making it look like school work.
Write in shaving cream , pudding, or finger paint. Yes it is messy but so much fun! Use shaving cream on the bath tub walls while your children are taking a bath.
Aqua doodles and magna doodles are a great way to practice and can even be used in the car.
Flatten play dough and write letters, numbers, and shapes in it with the back of a paintbrush or straw. Roll your play dough and form letters, shapes, and numbers.