Anyway, while doing some research I discovered that the National Education Association actually offers interactive math lessons and games for free online. But even better is the fact that they offer them in English AND Spanish! The Spanish version even allows you to choose the system of measurement that you prefer (such as U.S. standard of measurement or the Latin American one). You can also purchase all the lessons on a CD in either language.
The site allows you to narrow your focus by grade level and provides ideas for hands-on activities. And each grade is divided into sections covering the concepts that are required for each level. I think the games could be made a little more visually pleasing and fun for children. But the basics are covered in a simple way.
Anyway, I think this is a good site for supplementing your lesson plans and the games are good for reinforcing concepts. They also offer lessons in other areas like spelling and geography. So stop over there and test it out for yourself!
Con mucho cariƱo...