For $10, you can pick up a very very basic refractor with a flimsy tripod mount at any CVS. This will let you look at the Moon, Jupiter, and Saturn, which are the most interesting things to look at without going up several orders of magnitude in price. It's dead simple to set up and focus, and the challenge of wrestling it into position so you can see the planets, and see them move away as the Earth rotates, will give you the chance to teach reasonably mature kids about basic astronomy and to gauge their interest without spending a lot of money. If you live in particularly dark country, you can just barely begin to see things like the Orion Nebula with this kind of scope (though it looks like a smudge--we've all been spoiled by nice pictures from 2m+ telescopes mated to CCD cameras).