Well, pre-printing labels is one option I think I've seen discussed before. However, I am curious about the venue you're using - is it that you don't have access to a network or no computer or both?
I know that it is not supported, but using a cellular card, laptop, etc may be an option to look into. If you have reliable cell service and a 3G card, this could work well enough to do check in while connected.
If not, then you may want to prepare labels and print a roster prior to the event. If you're using checkin to do this, the big disadvantage would be undoing the check-in process for children who did not attend. If you're using something else for labels, then you could use your rosters to do post-attendance.
You may want to browse through the past posts. I remember this topic, but do not know if it was directly from another customer or by reading about it here.
In Him,
-Peter Schott