Have you talked to anyone on the park staff? There will be someone who is intimately familiar with the situation and who can provide very detailed information. I looked briefly at the park's web page and I noticed that at least two water sources within the park are off limits for human consumption and are reserved for wildlife.
I have never been in Guadalupe, but I have a lot of experience in arid land hiking (Arizona) and what you are proposing sounds pretty formidable. In a best case situation, you will need a minimum of three gallons per person. That's roughly 25 pounds of water. Adding in other gear, you are looking at a pretty tough trip especially for young lads who are relative beginners and who may not possess a lot of ULUE (ultralight, ultraexpensive)gear. If I were introducing someone to the joy of backpacking, I would choose a trip where water would not be an issue.
It will be interesting to see what info the folks in the park can provide, but I would seriously consider alternative trips. Within the Lincoln NF, particularly around Cloudcroft, New Mexico, there is some delightful, well watered country. I had a great trip there a while ago - no concerns about water at all.