At young ages, most children are really interactive. They can’t sit still for very long and have short attention spans. Insha Allah I wouldn’t personally worry about too structured teaching at really young ages. One can teach his/her child very naturally about Islam.
Teach duaas naturally. When you eat have him/her say Bismillah. When he/she goes to the bathroom have them say the duaa. Let them hear you say duaas throughout the day. Sometimes they amazingly pick up duaas (and some quraan) without formal instruction, by hearing them repeatedly, consistently.
Teach simple adab/hygiene. Eat with your right hand. Make istinja after using the bathroom, etc. From experience, I have learned that it is easier to teach these skills while they are young. When they are older, they get set in their ways and it is more difficult to correct “bad” habits.
Children love to be read to. Read the Quraan, Stories of the Prophets, ahadith and talk about what they mean. Ask them questions about what you read. Answer their questions. Try to paint pictures in their heads about what you are reading.
Teach them basic aqeedah. At 18 months I started teaching my youngest daughter and now my youngest son to respond to “Ayn Allah?” Where is Allah. Of course they don’t really understand the meaning at this point, but when I ask him where Allah is, he points to the sky (well, if he is laying down he may point off to the side, but the foundation is being set for when he is older, insha Allah.
Just take your daily routines and remember Allah much and teach them how to do things Islamically. Explain why you do this and that. (e.g. We start putting on our shoes, brush our hair with the right because the Prophet (salla Allahu alayhi wa sallam) did this. When you see them eating with their left hand, respond with the quraan or ahadith, like, ash- shaytaan yakul bis shamail. The shaytaan eats with his left).
Those are just some of the ideas that I had. Life is full of lots of “teachable” moments that don’t require worksheets and textbooks. Take advantage of them! (I am saying that to remind myself as well).
I have lots of posters and printables for Islamic Studies for older children at http://talibiddeenjrtoo.amanahwebs.com/is_home.htm