I will be doing day hikes on Kepler Track and in Te Anau --I have used my keen hiking sandals which have toe guard protection and they are very supportive and sturdy.. If I had to do some very rocky trails though I might not want to hike in them.. I have hiked in Sedona with them without a problem as I am not familiar with the trails I was curious to get some opinions as I do have hiking shoes but due to weight and bulk would prefer not to take them unless I need to
It's up to you. I did just fine with only cheap runners, but I prefer the minimalist/lightweight thing. Some people insist on clunky boots with ankle support, which I personally dislike.
Trails are generally well defined with packed down soil.

The Kepler track is in excellent condition. The track builders seem to have learnt from having built the Milford and Routeburn tracks and as a result the Kepler is really well drained and tends not to get so muddy. Be aware though tha the effect of this is that it's a hard surface throughout. But if you've used sandals before you should have no problem.

Their hiking sandals are much more heavy duty with good ankle support than ordinary street sandals. Apart from a piece at the back, they're almost a full shoe.
Sandals with ankle support?
Any sandal no matter how 'heavy duty' they are, by their very nature do not give any support to the ankle.
Hiya!
My Prada sandals with platinum toe stud inserts have sufficient ankle support. I've trekked up Mt. Victoria and all over the New Territories in them. You get what you pay for.