Well, waxing them is certainly less expensive than polyurethaning them, especially if you can't sand them beforehand. You need to clean them first with a good wood cleaner like Preen, then apply a thin layer of liquid or paste wax, let it dry to a haze and then buff with a felt pad followed by a lambswool pad for a higher gloss. The great thing about waxing is that if you get a scratch, you just fill it in with a colored wax stick and buff it right out. An electric buffer is pretty inexpensive, and easy to use. Just make sure your girls don't run on the floors in fluffy socks, unless they like to slide.