My brother went to Carlsbad Caverns as part of his senior trip many, many years ago. He said it was beautiful and brought back over 3000 slides. (He was part of the AV dept.) He said if you go west you need to make sure to stop at the Big Texan Steak Ranch in Amarillo, Texas. It's not too far from Carlsbad, NM. They have a 72 oz steak, that if you eat it, it's free. See it here:
http://www.bigtexan.com/free72.html
Use every opportunity to charge camera batteries that you can. Take lots of pictures. I'll never get there and would love to see it. I have to live vicareouly through others at times.
Enjoy your family time. And make memories!