So, the grandkids are coming for a visit and you haven't entertained toddlers since your own kids were little. Before panic sets in just remember that you really do have a lot to teach the little ones and that learning can be fun. Try a themed visit -- How about an Old MacDonald Had a Farm morning?
Start off with singing the song with your little ones and if they don't know it yet, teach them! Singing together is a wonderful way to build a bond. Next, grab some magazines and some safety scissors and have the kids look for pictures of farm animals. Cut them out and paste them on 3"x 5" cards.
Have the children identify the sound each animal makes and write it on a card with a marker. Play a game with the kids where you show them the card and they make the sound. Since they have already learned from Old MacDonald that a cow goes "moo" and a pig goes "oink" they should be able to master this fairly quickly.
When you have a short break, hide the cards in easy to find places and take the kids on a hunt to find them all.
Keep the cards for their next visit or send them home. They will remember you every time they see them.