We went Ala Carte instead of a package. Since my wife doesn't dive it seemed to be quite a bit cheaper that way. Found a rental car from Alamo for under a hundred a week.....added the insurance however since I have never driven on the wrong .....er left side of the road before!
I suggest bringing a GPS and car charger with you. Driving around Compass Point won't be a problem because there isn't much traffic and only a few main roads. But driving to and from the airport and visiting George Town and Seven Mile Beach and other parts of the island can be confusing. There are lots of roundabouts and George Town has many narrow, angled, one-way streets and traffic can get heavy during rush hours.
And you won't want to use up your cellular data and incur roaming charges by depending on your interactive phone maps. But some folks like to download the Grand Cayman maps to their phone before leaving home and say that works for them.
We have an old Garmin GPS and car charger and it works well for us, the Cayman maps are included in the North American Garmin map so you don't need to buy anything special. If you don't have one perhaps you can borrow one or buy one cheap on ebay? Garmin's international office used to be located on GC so they have good maps of the island.
In fact, the directions to Compass Point suggest using a Garmin GPS, see below:
Directions