With kids that age, you are wise to simply take advantage of teachable moments.
Simply interacting with them as they lead the way is the right idea. Take your cues from them and add in little tidbits of education when THEY bring it to your attention.
They don't have very long attention spans so in-depth things are not ideal. Just spend a lot of time stating the proper names of the items they are playing with and interested in.
FOr example when buiding a block tower with them, you can talk about how many blocks it takes or which tower is shortest or blue etc....lots of teachable moments in any type of play.
Promote ALOT self-help skills and proper indetification of objects, body parts, colors, shapes and words.
Remember.... Play IS learning!
