They have creative minds just awaiting stimulation. You just need to be imaginative when you are with your children and there are many opportunities to expand their learning skills. Even with crafts you can incorporate many learning skills. Colors, letters, motor skills. Having a chalkboard setup in the kitchen can keep them busy learning while you are attending to household demands.
Fridge magnets are fun for kids, they are available in the shapes of numbers and letters.
Try to remember, when talking with your child you can turn their curious questions into an in-depth discussion, and they benefit from this greatly. If you have a computer at home there are many websites available for kids. A good time to make use of this is when you have paper work, bills etc, to take care of. You can sit at your desk and tend to your business while your child plays computer games. This way you are available to help them while they are learning.