And that's all we needed. We then played around with the board and the numbers. The first time, I placed all the multiples of 10 on the board for him (10, 20, 30, 40, etc) so he would have some reference points for filling in the rest. I then gave him nine numbers at a time (1-9; 11-19; 21-29) so he would not get overwhelmed and could just concentrate on filling in one line at a time. After doing that once, we played around a bit with filling in multiples of 5. As we placed numbers on the board, he (and I) started to see some useful patterns. Even though he felt like he didn't know the names of all the numbers, he could start to tell what the next number should "look" like.
Now that he has seen a little bit of how it works, Ben is looking forward to trying out the "real thing" at school. We'll see what he comes home to teach me this week!