It may work, if they can adjust it to a group of adults. There should be no “59 years old, but going on 29 years old pretentiousness in their stage attire, or choreography. The harmonies will need to be condensed or simplified, because I doubt the ladies can sustain those high octaves for a complete four-measure tone. Look at poor Linda Ronstadt, I believe she has stopped singing in public, because of memory trouble. Good luck to them though, many people still like the cheery feeling of ABBA. One of my favorites was “Fernando”.
One of my favorite groups is The Seekers, and Judith Durham's voice is divine. She left the band to so a solo act...they broke up, and a few years ago they reuninted for a 25th anniversary tour.