K.B.
Your children are learning every minute of their lives. If you want your children to learn, talk to them, read to them, sing songs to them. There is really no magic potion for children. But the best thing you can do is introduce them to the world around them. Explain everything you do, they do, and they see. The little ones are like sponges, and even though they may not verbalize right now they will. Sign language is also helpful, I use the Sing in Time series. But as my developmental pediatrician reminded me last month, you have to make sure your children learn to verbalize.
so in summary read, sing, speak, and sign the same songs over and over, and read the same books over and over. But keep it fun, if it is too structured everyone ends up frustrated.
P.S. I just recently changed careers from being a classroom teacher a few months ago, so I do highly encourage anything that can build language and literacy skills.