I have gotten plastic disposable tips from a site called -onestopcandle.com- interesting mix of items. on the site click baking then decorating bags and tubes. They are about .50 each.
I wouldn't want to pay .50 cents a piece plus shipping for throw aways..when I can get wilton tips for .85...at least you will have a bunch handy.
Depending on how many kids...why not just cut the baggies? (if you don't need a detailed design)
The book Hello Cupcake shows what I'm talking about, here's the link...flip until it says page 14
http://www.amazon.com/dp/0618829253/?tag=cakecentral-20
Check at Michaels, or your local grocer, but I have seen disposable tips that work with the tubes. You may be able to use those in some way if you don't plan on using the tubes.
Quote by @%username% on %date%
%body%