I second Tony Hinds. He does a grocery stop if requested which I really liked.
Cabana Bay is across the street from Sapphire Falls, so you would pay a similar amount for Uber. We are staying at Sapphire Falls this trip, we really liked it walking through it last year. My DS really loves the boat ride to city walk.
If you are only planning on Universal/Islands and Discovery Cove, I would do what Bobbie 68 is suggesting. If there is a lot of off site stuff you like to do, it makes sense to get a car.
Also, I have tried looking into Universal’s airport transportation. Unless something changed it seems you need to book the transportation as part of a package. It doesn’t seem bookable separately.