With K's Pre K, I try to have some activities that she can do alone, and some that we do together. Today she had to trace her name with buttons, by herself, and come get me when she was done. It helps her to stay on task and complete projects, along with name and letter recognition, but it also allows me 10 or 15 minutes to spend helping the other kids, or to get something done.
The activity that she chose to do together was to play HiHo Cherry O. We had Tiny T down for a nap and the other 2 were playing another science based game, and we just spent the time together learning the game. It was great fun!