score:5
It's absolutely okay. These are the sites which most short-stay tourists visit and the roads between them are very good. I drove almost the same route in April. On a "mini" car class you usually are not allowed to drive into highlands but there are no such areas on your route.
And there are enough gas stations along the road so you can tank at any point of your route.
Upvote:3
I have been to iceland twice. It is totally ok to have Economy (e.g. i10) if you are doing Golden Circle and Southern Iceland to Vik. I booked i10 but got i30 because the rental company didn't have i10 at that time.