If you can see the summit of Mt Ruapehu take a detour via 47, not the desert road. Then up 48 and take the ski lift up to the highest cafe and enjoy the amazing views. The ride with the ski lifts was a great experience (even for our 6 years old) and we were lucky enough to see Mt Taranaki in the distance. Family pass for the ski lifts was 77$ and worth the money. On low wind days consider protection against these nasty sand flies.
If you own or manage Mount Ruapehu, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.