I think it is never too early to learn. Don't be surprise but there are already magnetic placards in my home. To be honest, I was wondering what to do with the bomb shelter door. We didn't do any works to cover it so I was considering a mural (which my husband disagrees because the design can't be changed in future).
This is how my bomb shelter looks like now and I think they look da bomb (no pun intended). The placards are from Learn & Love. They have a few series. Depending on your choice, it can cost between $15 to $22 for more than 20 pieces. In terms of design, my favourites are "The Loving Family", "I want to be..." and "Actions and Activities".
For now, baby is quite young. We would carry him and point to him the words etc. Sometimes, we would also point out other areas such as colour, body parts etc. Apart from mandarin, we would also verbalise to him in English. When he is older, we can probably mess the cards and let him match them back. He can either do it on a magnetic surface or on the floor.
Surprisingly, my friends are the ones using the cue cards to test each other when they are at my house. To be honest, we haven't been reading/ writing mandarin for the longest time. Yup, these has also ended up as "educational" drinking props. Can't write the word in mandarin, drink a glass! Once we are done with them, we attach them back the bomb shelter door. :P
Pretty good investment for families with young kids if you ask me, not only do the children get to learn. The friends of Daddy and Mummy get to brush up their Chinese a little too!