Here is a free grapic that will let you kids visualize how many pints in a gallon.
I'm a very visual person, and so are my kids, so I try to draw something out whenever I think creating a visual will help get a point across better. I find that sometimes just writing something out as a "picture" helps my children remember the information better, too, even if it's a simple concept to start with.
Last year we were studying measurements of volume in math, and my kids were having trouble remembering all the volume units and their relationships. So I drew this simple diagram, which has actually helped me remember volume relationships much better, too. It worked wonders.
You can download the black-and-white "How Many Pints in a Gallon?" graphic or the color "How Many Pints in a Gallon?" graphic for your personal use. Hopefully this free grapic will help you never to forget how many pints there are in a gallon.
If you find this helpful, you might also like to download my Cooking Measurement and Conversion Chart.