Because of their ages I would be doing my "lessons" in the midst of play as compared to a separate time. Then when they seem to be starting to actually pick up the information make it more focused. Example play with the blocks and name the colours, ask a child to hand you a "red" block - if they don't show them which ones are red, etc. Count how many cars are lined up and then send them down the ramp one at a time. Name the farm animals and the sounds they make and sing old macdonald had a farm as you do.
I don't do a lot of crafts with my group because it requires too much of me doing it or being right there with each one as they do it although we do colour with crayons and playdough etc.
This is a good age to introduce the feltboard because you can leave the pieces out and while not recommended as teething toys can take a lot of toddler abuse. Then gather them around the board for a "lesson" or if someone shows interest start with them and gradually others will get in the habit of drifting over. Continue as long as there is interest. Put up some seasonal things or shapes in assorted colours to be sorted, matched, etc.