Spa Treatment

My sister and I want to send our parents to Montana to as a Christmas gift. They’re both really into the nature-based scenery, and we want to give them a few days of relaxation. Any suggestions?
I’ve searched on numerous travel websites, but I could never find anything better than a 3-star hotel.
I’ve been searching using spafinder.com but some personal experiences/input would be great.

Julio - faucet water filters

UPDATED : Destination La Costa Spa

I only seem to find resort spas, but not an all inclusive package geared toward jump starting a health program. Help?

Ligia - spa certificates

UPDATED : Dreams Spa & Resort: A Luxury Travel Destination